UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Other Discussions > Homebrew Equipment

Notices

Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members.

Reply
 
Thread Tools
Old 4th Jan 2023, 5:17 am   #401
dmowziz
Pentode
 
Join Date: Nov 2021
Location: Toronto, Canada
Posts: 130
Default Re: 6-gang FM stereo tuner heads

Quote:
Originally Posted by regenfreak View Post
Quote:
Originally Posted by G0HZU_JMR View Post
The single diode limiter (with a bias choke across it) probably isn't a good choice as a protection limiter. It won't offer very good isolation for large signals. A better limiter design will use four diodes arranged as a classic clipping limiter.

A typical silicon diode will have a forward voltage of about 0.8 to 0.9V when biased hard so the clipping limiter will produce a rounded square wave output at about 1.8Vpkpk when hard limiting. Hiding inside this 1.8Vpkpk rounded square wave will be a fundamental sine wave of about 2.3Vpkpk (or 1.15Vpk)

This will produce a through leakage power of (1.15^2)/100 watts into a 50R load when hard limiting. This is about +11dBm at the fundamental frequency. That's what you can expect from a classic 4 diode limiter. Some limiters only use two diodes, and this can help extend the bandwidth to >2GHz. The 2-diode limiter won't be as rugged though.

I'm a bit out of date when it comes to the capability of modern limiter diodes, but 15-30 years ago a well-designed silicon (4) diode limiter could withstand a 5-10W incident power (without damage) whilst limiting the leakage to less than about +13dBm. The limiter should be transparent to signals that have a maximum amplitude that is in the order of <0.6Vpkpk. i.e. the limiter should not cause any significant distortion to waveforms smaller than this.

Thanks. The 4 rectifier diode idea is still in my mind but I am concerned about the large diode junction capacitance which may call for a matching network to tweak the S11 and S21 at high frequencies.

I have taken another potshot at the PIN diode. I ordered a Skyworks SMP1330-005LF last night. It is a PIN-Schottky pair, having a threshold about +10dbm, C=0.7pF, 14db attenuation at +30dbm working up to 4GHz (see power characteristics attached). I speculated that the cheapo pin-limiter does not work well because it uses only a single diode PIN diode.

https://www.skyworksinc.com/-/media/...es_200050N.pdf

I am going to add two 1kV 1206 10nF and 250mA SMT fuse plus a 70V 4532 SMD ceramic GDT (capacitance = 0.5pF) to safeguard against "catastrophic event". I will house them in RF shield instead of using a metal box.

I have been looking at the integrated SKY1662-632LF datasheet:

https://www.skyworksinc.com/-/media/...LF_202945L.pdf

It is kind of interesting to see how they put a simple series LC network to optimize the S11 and S21. With L = 1.8nH, C=15pF for 2.45GHz, they transpose the peak and trough for S11 and S21 to the right. The equivalent circuit of a PIN diode (in open state) is like a small inductor in series with the paralleled capacitor and a very large resistor. The S21 and S11 look a bit like a very broadband bandpass filter.


PS: I have received the ATC caps and other goodies that you sent. Thank you so much. I am building a "Q detector probe" with your ATC 1pF caps. It will use FET MMBF310 and MMBF3906 as impedance convertor. The device will be used to find approx Q and resonance frequency of air variable tuning gangs and IF transformers for MW, SW and FM radios in unpowered state.
The ATC100 series caps have Q about 10,000..quite badass!



Just wondering,

Please the big things that look metallic.

Are they the capacitors? 1 of them is 1 capacitor?
Attached Thumbnails
Click image for larger version

Name:	RF shields.jpg
Views:	56
Size:	37.3 KB
ID:	270865  
dmowziz is offline   Reply With Quote
Old 4th Jan 2023, 4:20 pm   #402
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

[QUOTE=dmowziz;1525766]
Quote:
Originally Posted by regenfreak View Post


Just wondering,

Please the big things that look metallic.

Are they the capacitors? 1 of them is 1 capacitor?
They are low-profile Faraday cages/ metal shields for SMD circuit boards that come with mounting clips. They are handy for high-frequency or microwave circuits and are cheaper alternatives to the metal housing.
regenfreak is offline   Reply With Quote
Old 4th Jan 2023, 4:37 pm   #403
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,458
Default Re: 6-gang FM stereo tuner heads

They aren't Faraday cages, the metal is solid, so they also act on magnetic field components. Faraday screens are special, they are aligned grids of wires designed for purely electric field screening and are pretty much useless for general screening duties.

The idea behind the wire grids is that there is no path for circulating eddy currents.

This is a very common confusion, but it's wrong. You'll find real faraday screens inside some transformers to block capacitive coupling between windings.

These things are simple metal screening boxes, often plated steel or brass. They get soldered onto printed circuit boards over an area of componets doing something sensitive. Often the PCB has a groundplane area which acts as the lid, completing the screening box. They are a right pain for fault finding and access. They need a bigger soldering iron to remove them than they take to fit!

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 4th Jan 2023, 7:02 pm   #404
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

Quote:
Originally Posted by Radio Wrangler View Post
They aren't Faraday cages, the metal is solid, so they also act on magnetic field components. Faraday screens are special, they are aligned grids of wires designed for purely electric field screening and are pretty much useless for general screening duties.

The idea behind the wire grids is that there is no path for circulating eddy currents.

This is a very common confusion, but it's wrong. You'll find real faraday screens inside some transformers to block capacitive coupling between windings.

These things are simple metal screening boxes, often plated steel or brass. They get soldered onto printed circuit boards over an area of componets doing something sensitive. Often the PCB has a groundplane area which acts as the lid, completing the screening box. They are a right pain for fault finding and access. They need a bigger soldering iron to remove them than they take to fit!

David
I see. The real Friday cage is often found in tesla coil demo where people stand inside;

https://youtu.be/Lqwj5bACKbU

The shields i got have clip-on bits that you are supposed to solve the de-soldering problem you mentioned.
regenfreak is offline   Reply With Quote
Old 4th Jan 2023, 11:06 pm   #405
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,458
Default Re: 6-gang FM stereo tuner heads

Some people suggested that the magnetic induction transformer was actually coupling energy capacitively. So Faraday invented his special shield, which blocks electric fields only to prove that the coupling had to be magnetic.

Unfortunately, some people automatically prefix the word screen with Faraday's name. Maybe they think it makes the screens appear screenier? But in reality from the point of screening radio signals, Faraday screens leak like a seive. It's comparable to prefixing every mention of the word 'Tyre" with the word "flat". But Faraday screen/cage/shield seems to have entered folklore. Lexicographers have their dictionaries change to follow newer usage, but this is science and we are talking specific and defined terms here where we can't let meanings change without trashing knowledge.

Not being grumpy, just trying to defend something we need for accuracy.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 5th Jan 2023, 12:06 pm   #406
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

Quote:
Originally Posted by Radio Wrangler View Post
Faraday screens leak like a seive. It's comparable to prefixing every mention of the word 'Tyre" with the word "flat". But Faraday screen/cage/shield seems to have entered folklore. Lexicographers have their dictionaries change to follow newer usage, but this is science and we are talking specific and defined terms here where we can't let meanings change without trashing knowledge.

Not being grumpy, just trying to defend something we need for accuracy.

David
The levels of H- and E- fields penetration vary significantly with frequencies, see attachment. Above 100KHz, the W- and H- field converges into plane waves over a wide range of frequencies...The rule of thumb is that the grid spacing is about 1/10th of the wavelength.
Attached Thumbnails
Click image for larger version

Name:	E -H field attenuation Faraday cage.jpg
Views:	31
Size:	97.6 KB
ID:	270937  
regenfreak is offline   Reply With Quote
Old 5th Jan 2023, 4:27 pm   #407
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

Incidentally I have been digging through the Black Hawk helicopter aerodynamic performance data ( to do with my job), I have noticed that there were 5 crashes caused by the Black Hawk flying close to radio broadcast towers. Subsequently they improved the EMI shielding of the avionics and flight controls. There were many similar incidents for other fixed wings and rotary wing vehicles in this NASA report:

https://ntrs.nasa.gov/api/citations/...9960009442.pdf
regenfreak is offline   Reply With Quote
Old 5th Jan 2023, 4:27 pm   #408
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,458
Default Re: 6-gang FM stereo tuner heads

Distance gets in on the act too. Far field in normally taken as 20 lambda from a source. Within that area, as you get nearer the source, you can find predominantly one field more than the other. Another factor is skin depth and then there is the permeability of the shield.

However, use of the prefix - Faraday takes care of all that and specifies a shield designed to pass magnetic components. And as we all learn in trying to screen things, electric components aren't too bad, it's the magnetic ones which are the devils.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 5th Feb 2023, 5:23 pm   #409
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

Before Christmas, I wrote that I was going to build another 6-gang tuner with an unbalnced dual gate mosfet mixer because I have three of the same military, silver-plated 6-gang air variable capacitors.

The attached schematic is the finished version 2 tuner. The design is very similar to the first version with a BJT mixer except it uses one inductive coupled tunable BPF and one capacitive coupled tunable BPF in the RF amp stages.

Everything performs well as expected. The local oscillator has a buffer amp that drives gate 2 at a much higher signal level than the RF input from gate 1. The transconductance is amplitude modulated by the local oscillator "pump" voltage (see attachment 5). I installed a digital frequency display like the first version. It is getting harder and more expensive to obtain the original vernier tuning dial knob so I have used a cheapo chinese alternative which is over 180 degrees of rotation. It works Ok but not as good as the originals.

My next projects will be the experimentation with a balanced dual gate mosfet mixer which is more difficult to implement.

I consider building a 8-gang varactor tuning FM receiver...I have some ideas floating around but I nowadays spend much more time keeping fit since the start of the year and spend less time on electronic projects.
Attached Thumbnails
Click image for larger version

Name:	6 gang dual gate mosfet   v2.jpg
Views:	71
Size:	71.1 KB
ID:	272739   Click image for larger version

Name:	6 gang v2 A.jpg
Views:	64
Size:	82.7 KB
ID:	272740   Click image for larger version

Name:	6 gang V2 C.jpg
Views:	63
Size:	80.8 KB
ID:	272741   Click image for larger version

Name:	6 gang v2 B.jpg
Views:	53
Size:	92.5 KB
ID:	272742   Click image for larger version

Name:	DGMFET osc transconductance.jpg
Views:	38
Size:	40.9 KB
ID:	272743  


Last edited by regenfreak; 5th Feb 2023 at 5:29 pm.
regenfreak is offline   Reply With Quote
Old 12th Feb 2023, 3:32 pm   #410
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

One of the most difficult challenges of making a multiple-gang varactor tuned broadcast receiver is the linearity and predictability of the tracking. I have done some measurements to characterise the Philips BB204B double varactor diode in terms of their frequency linearity, unloaded Qu in an LC tank and their actual performance in a tunable bandpass filter.

Based on the datasheet, I think its graph was measured with one of the two diodes. One diode Q is about 200 at 100MHz. In my case, I have measured diode capacitance with two diodes in series which would half the Q to about 100. The advantage of having the diode in series is that it minimises the effects of the fluctuating RF AC on the diode capacitance and less distortion products.

The mathematical model of the varactor is represented by the simple equation in attachment one. V is the sum of DC tuning voltage plus RF signal voltages. Phi is the contact potential of the diodes. By taking the logarithmic function of the C and V relation, it is possible to find the power index n using linear regression.

The varactor can be idealised as a capacitor (of high resistance depleted region) in series with a small value resistor (variable, low-resistance undepleted region+ constant contact resistance). Q increases with increasing reversed bias voltage, therefore its performance should be worst at the lower limit of the broadcast band.

Attachment 2 illustrates LogC vs log(V+phi), the power index n = 3.37 using linear regression. For ideal linearity, n should be 2 because the frequency is inversely proportional to capacitance squared. I have found there are variations of the measurements among different BB204B samples.

In the 3rd attachment, it shows the measurements of (1) frequency vs reversed voltage and (2) unloaded Q of LC resonator vs frequency for a single LC resonator (L =88nH). In this scenario here, the Q of the inductor is comparable in magnitude with that of the varactor diode (1/Q = 1/Qc + 1/QL). Usually, the Qc of the air gang capacitor is significantly bigger than the inductor QL.

AT 88Mhz, Qu = 55 and at Qu = 129, very drastic difference!


To evaluate the performance of the varactor diodes in a tunable FM bandpass filter with 50 ohms terminations, I have tried it with a Butterworth optimised at 100MHz. As you can see in attachment 4, it smashes at 50 ohms; bang on at the centre of the Smith chart. S11 = -45db, S21 = -2.5db which is very good (typo in my file name, it should be 98.8MHz and not 86.8Mhz)

Attachment 5, shows the changes in bandwidth and bandpass response at 88Mhz, 99Mhz and 108Mhz, respectively. At 88Mhz, the filter has about additional -2db insertion losses due to the lower Q of the varactor diodes at the low-frequency bottom end. At the top end of the broadcast 108Mhz, the selectivity of the bandpass degrades and therefore it is desirable to have multiple gangs of tunable bandpass filters in high-performance FM tuners.
Attached Thumbnails
Click image for larger version

Name:	Q undepleted resistance.jpg
Views:	23
Size:	55.1 KB
ID:	273147   Click image for larger version

Name:	BB204 logC vs log(V+phi) n=-3.37.jpg
Views:	16
Size:	40.3 KB
ID:	273148   Click image for larger version

Name:	BB204 f and Q vs V.jpg
Views:	14
Size:	37.7 KB
ID:	273149   Click image for larger version

Name:	BB204 86.8MHz -2.5db 50 ohm.jpg
Views:	15
Size:	44.6 KB
ID:	273150   Click image for larger version

Name:	BB204 varactor tuned bandpass.jpg
Views:	18
Size:	54.9 KB
ID:	273151  


Last edited by regenfreak; 12th Feb 2023 at 3:56 pm.
regenfreak is offline   Reply With Quote
Old 12th Feb 2023, 7:35 pm   #411
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

I have been suspicious about the value of n =3.73 in my previous post. I would expect n to be between 0.3 to 2. I have checked a 1967 IEEE paper, the previous equation only applies to a single varactor diode. Therefore I should have repeated the measurement with only one diode to obtain the correct n from the slope of the Log(C) vs Log(V+phi) graph.

Based on R. De. Cola's IEEE paper "Varactor Tuning applied to Am-FM receivers", the model of two back-to-back varactor diodes are rather complicated as shown in the attachment. In this case, it is not possible to find n using linear regression.

BTW the IEEE paper is full of maths and quite difficult to understand.
Attached Thumbnails
Click image for larger version

Name:	back to back varactor diodes.jpg
Views:	20
Size:	42.3 KB
ID:	273181  
regenfreak is offline   Reply With Quote
Old 10th Apr 2023, 6:37 pm   #412
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

Making a high-performance varactor-tuned FM receiver has turned out to be a labour of love. Achieving perfect tracking of multi-gang is far from a trivial problem. This involves matching varactor diodes from a modest size of samples and accurately measuring their capacitance using appropriate test jib and LRC meter. Typically VHF varactor diodes from the same factory batch can have capacitance deviations as large as a 2 pF to 5pF at the lower end of the reverse-tuning voltage. A few pico Farads will throw off the tracking calculations completely. To get them tracked with unmatched varactor diodes is like a dog chasing its tail.

To illustrate how accurate a commercial FM tuner is in varactor tuned tracking, I measured the tracking error (fosc-f-10.7 MHz) of my Pioneer F99X. As shown in attachment one, the tracking error is very impressive, a maximum of 20kHz with PLL tuning. Most high-ended FM tuners with varactor-tuning gangs have fewer than 5-6 gangs because of the diminishing returns. The diode distortion products are worse than air variable capacitors.

In attachment 2. I measured the linearity of my VCO with BB204 varactor diodes in an anti-series configuration.

I have experimented with the measurements of very small inductance, the unloaded Q of VHF inductors, the distributed capacitance and SRF of coils using a NanoVNA. I have made a set of calibration standards that eliminates the distributed capacitance/inductance of the test jig, moving the measurement planes as close as possible to the tested coils. I validated the test jigs using 1% 1206 Coilcroft coils and Toko VHF coils of 100Hn. The measured inductance unloaded Q, and SRF agree well with the published data.

Attachment 3: measurement of the SRF of a 111nH inductor made of 1mm diameter silvered plated copper wire with an inner coil diameter of 5mm. The inductance is measured with shunt S11 measurement. The SRF is 576MHz when it crosses over the real axis of the Smith chart. The distributed capacitance of the coil is estimated to be 0.7pF at 100MHz. The corrected inductance is 107.7nH at 100MHz after considering the distributed capacitance.

Attachment 4: is the measurement of unloaded Q of the same 111nH coil in series LC resonance with a 24pF AT100B high Q capacitor. The VNA measurement is in shunt-through mode. The Qu is about 202 at the resonance frequency of 95.67MHz.

Attachment 5, S11 and S21 of the shunt series resonance circuit. At the resonance frequency, the impedance is very low. The shunt series LC method seems to give the least error in measurement. I added a 3db attenuator at port 2 to mask the impedance mismatch, which tends to rear its ugly head in low-impedance through transmission measurements.
Attached Thumbnails
Click image for larger version

Name:	Pioneer F99X tracking errors.jpg
Views:	17
Size:	42.4 KB
ID:	276619   Click image for larger version

Name:	BB204 VCO linearity.jpg
Views:	17
Size:	30.9 KB
ID:	276620   Click image for larger version

Name:	111nH silver SRF 576MHz Cd = 22.8 div 32.12 =0.7pF at 100MHz Lt= 0.97Li=107.7nH.jpg
Views:	17
Size:	37.3 KB
ID:	276621   Click image for larger version

Name:	111nH 95.67MHz Q = 202 shunt series LC.jpg
Views:	14
Size:	38.5 KB
ID:	276622   Click image for larger version

Name:	111nH 3db atten Rs 0.33 XL 66.72 Q = 202.jpg
Views:	14
Size:	32.7 KB
ID:	276623  


Last edited by regenfreak; 10th Apr 2023 at 6:55 pm.
regenfreak is offline   Reply With Quote
Old 5th May 2023, 9:43 pm   #413
nemo_07
Triode
 
Join Date: May 2022
Location: Cologne, Germany.
Posts: 28
Default Re: 6-gang FM stereo tuner heads

Quote:
Originally Posted by regenfreak View Post
Making a high-performance varactor-tuned FM receiver has turned out to be a labour of love. Achieving perfect tracking of multi-gang is far from a trivial problem. This involves matching varactor diodes from a modest size of samples and accurately measuring their capacitance using appropriate test jib and LRC meter. Typically VHF varactor diodes from the same factory batch can have capacitance deviations as large as a 2 pF to 5pF at the lower end of the reverse-tuning voltage. A few pico Farads will throw off the tracking calculations completely. ...
You don't have to measure capacitance values (then make calculations) when selecting for tracking. Instead, build an oscillator (like the one you will use in the front end), fitted with a socket for tested diodes (cut out from a DIL socket), an output buffer stage for frequency counter, and a provision for switching the tuning voltage to values of interest (say, 2V and 10V or so).
Note also that there are two types of BB204: the BB204B (blue) intended for RF stages and BB204G (green) for the LO:
https://datasheetspdf.com/pdf-file/4...lipss/BB204G/1
So you might build another one oscillator to make things easier.
There are better matched types made available in recent years, but mainly in SMD versions like BB814, for example.
nemo_07 is offline   Reply With Quote
Old 6th May 2023, 12:45 am   #414
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,458
Default Re: 6-gang FM stereo tuner heads

One of the most difficult tasks in design is in deciding when enough is enough.

The Q figures of varactors are inferior to mechanical capacitors. For equal selectivity, you get more loss, or for equal loss you get less selectivity. For a series of many RF tuned stages, with interposed amplifiers to make up for loss, you get the sums of all the compression effects of all the amplifiers, you get the sums of all the noise sources. You lose dynamic range at both the top and the bottom. So an infinite string will lead to zero dynamic range. Somewhere, well short of infinity, is the point where more damage is being done than had fewer stages been used.

The other demon which gets in is as you make the RF selectivity very tight is that you start to get non-flat group delay (= non-linear phase) across the channel giving distortion in the FM signal before it's even reached the discriminator. I have one Sony top of the range tuner which wobbles the tuning voltage to the RF stage varactors to try to track the deviation of the signal so that most of it finds the RF selectivity centred on it. Clever idea, but I'm not sure it's necessary but the measured distortion is pretty decent. There are comments n the internet that the units are a bit variable in performance and that only certain gurus can set them up well. It seems the market doesn't fully understand what Sony was trying to do.

Once upon a time I was involved in designing test gear for setting up FM mods and demods, where the carrier was on 140MHz, deviation could reach 40MHz p-p, the modulating baseband was 60kHz to 18.6MHz made of something like 2800 voiceband circuits modulated as SSB, oh and they wanted dynamic range (noise and distortion) to give approaching 80dB NPR across the channels. This meant a very finely balanced tradeoff amongst many impairments. Audio doesn't realise how easy it has it

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 6th May 2023, 11:49 am   #415
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

Quote:
Originally Posted by nemo_07 View Post
Quote:
Originally Posted by regenfreak View Post
Making a high-performance varactor-tuned FM receiver has turned out to be a labour of love. Achieving perfect tracking of multi-gang is far from a trivial problem. This involves matching varactor diodes from a modest size of samples and accurately measuring their capacitance using appropriate test jib and LRC meter. Typically VHF varactor diodes from the same factory batch can have capacitance deviations as large as a 2 pF to 5pF at the lower end of the reverse-tuning voltage. A few pico Farads will throw off the tracking calculations completely. ...
You don't have to measure capacitance values (then make calculations) when selecting for tracking. Instead, build an oscillator (like the one you will use in the front end), fitted with a socket for tested diodes (cut out from a DIL socket), an output buffer stage for frequency counter, and a provision for switching the tuning voltage to values of interest (say, 2V and 10V or so).
Note also that there are two types of BB204: the BB204B (blue) intended for RF stages and BB204G (green) for the LO:
https://datasheetspdf.com/pdf-file/4...lipss/BB204G/1
So you might build another one oscillator to make things easier.
There are better matched types made available in recent years, but mainly in SMD versions like BB814, for example.
I made an oscillator, and that's how I got the graph for frequency versus bias voltage posted previously. I was on the verge of finishing the 4-gang varactor tuned FM tuner..

I suspended this hobby last month and don't think I will go back to it in the near future. I think enough is enough. This hobby has become OCD-level and makes me very nerdy. I am sick and tired of hoarding radios and electronics and spending lots of money on ebay and Aliexprress. My home is like an electronic junkyard running out of space to live. I have been decluttering my home for weeks.

I have returned to my old hobbies: fitness and fashion photography. I did studio photography and retouching for 15 years. Aslo I shot gymnastics as a hobby at the international level for many years and got many published works. I used to work with an extensive network of models, make-up artists, hair stylists and designers. I still own a substantial collection of professional camera gears and photographic studio lighting. I found the radio and electronics to be a solitary hobby which served me well during the pandemic.Visiting this forum has been a pleasure, and I learnt a lot.

Once I started playing with electronics a few years ago, I lived like a hermit and stopped meeting new people. I used to be a well-round individual who likes arts. I feel I will waste my talent in photography if I don't get back to it soon enough. These days I prefer to hit the gym and go out walking. I put my health and mental health as first priority.
regenfreak is offline   Reply With Quote
Old 6th May 2023, 4:26 pm   #416
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 21,458
Default Re: 6-gang FM stereo tuner heads

There is much benefit in having a mixture of unrelated interests. Getting fixated on just one tends to leave people akin to a gravitational singularity.

Photography for me is fast-action sports with (currently) a D6. Exercise is on top of exuberant horses.

The vintage radio/audio stuff will still be here whenever you want to dip in. It's just one more string on your bow. You've found out all the trade-offs, compromises and insurmountable limitations hidden inside products consumers paid a few hundred quid for.

Whatever field you build up expertise in, there comes a point where you feel a need to pass it on to a new generation. Arty skills like photographic composition seem longer lived than consumer technologies.

The main thing is to have fun. For me, having electronics as a hobby allowed me to explore wider than the electronics job did. Whenever things got nastily political at work, the horses took me as they found me and kept me sane (well, sane-ish). Somehow through all this I got to photograph opera dress rehearsals for publicity shots, carriage driving, 3-day eventing, and aerobatics.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 7th May 2023, 12:51 pm   #417
regenfreak
Heptode
 
Join Date: Nov 2018
Location: London SW16, UK.
Posts: 655
Default Re: 6-gang FM stereo tuner heads

Quote:
Originally Posted by Radio Wrangler View Post
There is much benefit in having a mixture of unrelated interests. Getting fixated on just one tends to leave people akin to a gravitational singularity.

Photography for me is fast-action sports with (currently) a D6. Exercise is on top of exuberant horses.

The vintage radio/audio stuff will still be here whenever you want to dip in. It's just one more string on your bow. You've found out all the trade-offs, compromises and insurmountable limitations hidden inside products consumers paid a few hundred quid for.

Whatever field you build up expertise in, there comes a point where you feel a need to pass it on to a new generation. Arty skills like photographic composition seem longer lived than consumer technologies.

The main thing is to have fun. For me, having electronics as a hobby allowed me to explore wider than the electronics job did. Whenever things got nastily political at work, the horses took me as they found me and kept me sane (well, sane-ish). Somehow through all this I got to photograph opera dress rehearsals for publicity shots, carriage driving, 3-day eventing, and aerobatics.

David
Well said. Thank you for enlightening me on RF in the last few years. I didn't know we have a fellow accomplished photographer here. Yeah, I can always dip in and out of the radio/electronics hobby. But when I cannot manage to do it in moderation, I have to put a hard brake on it. I always struggle with work-life balance. This forum has been a refuge for me in the last few years, particularly during the pandemic. I have encountered lots of nasty work politics lately and was unhappy with my home's clutter.

It has been over 4 years since my last photo shoot. It was incredibly weird to pick up my DSLR camera for the first time a few weeks ago after 4 years. I thought oh my God what has happened to me? Almost a piece of me has been dying inside slowly without knowing it.

Luckily I don't need to spend any more money on photography as I invested heavily in the past, and I no longer shoot action. Action photography is very expensive, I used to own those white big beast super telephoto lenses like 300mm f2.8 and I still have the Canon 200mm F1.8L. I had to travel all over the world shooting gymnastics for magazines and federations- they issued me photojournalist passes and sometimes paid for my travel expenses. With fashion and studio photography, I stopped getting hung up on getting the latest and the best gear and focused on the creative processes and teamwork years ago.

I am a few years behind with all the mirrorless technology and am shocked that the Nikon Z7 can shoot 120fps. I shot the Athens Olympics in 2004, my Canon1D MK-II had 11fps which was cutting-edge, technology, you had to have good timing to capture the peak moment. With the Nikon Z7, you just do machine-gunning with the shutter button, requiring no timing and fast reflex. But then I was using film cameras like Mamiya RZ-67 Pro II and Canon EOS3 before the Millenium. Probably the SLR cameras will die soon and with be replaced by mirrorless cameras with lots of AI technology embedded. These days everyone is a photographer with their Smartphones and Instagram filters.
regenfreak is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 2:53 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2023, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.