UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio 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 26th Feb 2020, 7:41 pm   #1
Skywave
Dekatron
 
Skywave's Avatar
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 6,726
Question Idea for a method of Z measurement.

Since I like to 'do things' with R.F. circuitry, there are times when I would like to be able to assess impedance matching / mis-matching in a 50Ω system. To that end, I have a Telonic 'RHO' device. In use, you connect the reference Z to one port; the exciting source to a second port; the unknown Z to a third. This device has a BNC socket which delivers a d.c. voltage that is related to the degree of mis-match (or otherwise) between the reference Z and the unknown Z. In essence, this device appears to be a form of an impedance bridge.

Aside.
And yes: I do appreciate that it is 'old tech' - but it does seem to work! I am also aware that there are other methods / tools to meet the same requirement, but for now, I would appreciate any posts being restricted to this particular device: thanks.

I'm sure that this device could be used in a suitable circuit arrangement for a given 50 Ω system, with an analogue meter, calibrated in dB, to indicate the return loss.

Any ideas / suggestions etc. to meet that need using this device and in the described manner will be much appreciated.

Thank you.

Al.
__________________
Never act on your first idea. Like solving a crossword clue, a better idea arrives tomorrow.
Skywave is offline   Reply With Quote
Old 29th Feb 2020, 3:01 am   #2
G0HZU_JMR
Octode
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,839
Default Re: Idea for a method of Z measurement.

Back in my youth long before I had a network analyser I made a similar device for measuring return loss. In my case I wanted to be able to measure passive and active circuits so I designed for a very low level test signal of about -20dBm into the DUT. This required a wideband 50R MMIC amplifier ahead of the detector diodes to boost the signal up into the useful range of the diodes.

I wanted a low test level so I could test the input and output of amplifier stages without driving the amplifier into compression and -20dBm was a good compromise.

However, in your case you have a fully passive setup so it might need to be driven harder.
The first thing I would do is terminate Z2 in 50R and leave Z1 (test port?) as an open circuit.

Then feed in a 10MHz sinewave to the source port and make a chart of detector readings vs drive power level at 10MHz. I suspect that your device will use a very efficient detector diode and there may be an upper drive level before you stress the detector. This will probably be something like 200mW but I would keep it below 10mW to start with as this is probably the most you would be able to drive it with from a typical sig gen anyway.

I'm going to assume there is a single detector diode inside the box and this will rely on you feeding the test port with a reasonably clean sinewave with low harmonics. -40dB for the harmonics would be nice but -30dB will be OK and this is probably what you would see from a typical RF sig gen. If you can fit a 50 ohm 10MHz LPF after the sig gen to clean away the harmonics that would be a good thing for the calibration process below.

With the sig gen at 10MHz and 10mW (10dBm) write down the detector voltage and call this 0dB return loss.

Then step the 10MHz signal down in 1dB (prefer 0.5dB) steps over a 30dB (prefer 40dB) range and write down the detector voltages in 1dB steps down to 30dB. With luck this will be your return loss chart but this assumes the device works the way I expect.

Then repeat with a short circuit at the test port. Hopefully the chart for a short will be virtually the same as the open and there will be no need to write anything down. There may be minor differences but this is OK. However, if it is 'very' different with a short circuit then it may be the case that your RHO circuit is a bit different to what I would expect and all the above will be of limited use and I'll have to think again.

If all goes well then go back to 10mW drive level such that you again get the 0dB voltage at the detector port on a DVM. Then fit a 50R load and hopefully the voltage will fall to zero (off your 30dB chart).

Then fit a 100R resistor as the load and hopefully you will see a detector voltage that corresponds to 9.5dB return loss on your chart and this corresponds to a 2:1 VSWR load.

If you get this result then I think you can now use the device as a return loss bridge across a wide frequency range alongside the return loss chart. You may have to tweak the drive level to get your 0dB calibration with an open circuit each time you change frequency.

If the device really does work like the above then you should now have a calibrated bridge although you may have to be careful you don't overdrive any active (amplifier) stages as this will give false results. You may find you have to use it mainly for passive devices.

Alternatively, set the sig gen down to 0dBm and offset the chart 10dB and you once again have a return loss bridge but with reduced range. It won't be as easy to measure close to 50R with such a low drive level.

It is a very old device but it probably has the potential to be a very useful bridge over a huge frequency range. But to get the best from it you need to use a signal source with low harmonics or the harmonics can introduce significant measurement uncertainty at the detector and this will degrade things way below the full potential of this bridge.

Hope this is useful (and correct!)
__________________
Regards, Jeremy G0HZU

Last edited by G0HZU_JMR; 29th Feb 2020 at 3:09 am.
G0HZU_JMR is offline   Reply With Quote
Old 29th Feb 2020, 3:21 am   #3
G0HZU_JMR
Octode
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,839
Default Re: Idea for a method of Z measurement.

If it doesn't work like the above then maybe this device allows you to compare the impedance at Z2 (reference) against the DUT at Z1 where the Z2 reference can be a complex impedance. It could be a resistance in series with a capacitor or an inductor for example. The deeper the null at the detector the closer the agreement between Z2 and Z1. But this would be a fairly clunky way to do things and I'm not sure how often such a device would be useful.
__________________
Regards, Jeremy G0HZU
G0HZU_JMR is offline   Reply With Quote
Old 29th Feb 2020, 4:54 am   #4
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 13,311
Default Re: Idea for a method of Z measurement.

What frequency range do you want to work over?

Your 'RHO' device seems to be a 4-port hybrid with a detector built in on one port. It isn't difficult to make another hybrid, unless you want particularly wide bandwidth. I made one that covers the MF and HF bands using a couple of toroidal ferrite cores and a bit of wire. A signal source feeds one port (HF/MF transmitter) and a load (antenna) goes on the associated through line port. I happened to build it for 1/144th power sampling. 1/2 would have been possible and any other perfect square ratio, but I was intending this one to work to a few hundred watts. The two other ports produce separated samples of the the forward wave and of the backwards wave on the transmitter to antenna path. I put a pair of attenuators on the 'sample' ports and fed their signals to a pair of Analogue devices logarithmic detector chips.

The voltage from the logger on the forwards port drives a meter with a power scale on it... a linear scale of dB(Watts) which ought to make Ofcom feel happy
The other logger drives a meter showing dB(Watts) of reflected power. A meter reading the two logger voltages has a scale of return loss linear in dBs which is handy. So I have a computing VSWR meter with a usefully expanded scale.

Going the whole hog, the AD logger chips I used also had limiter outputs just itching to be used, so I added a bit more fast gain with some ECL line receivers, and built a phase detector in ECL logic. So I have a phase meter.

This amounts to having made a vector network analyser that monitors my transmitter to antenna path. I get return loss and phase, ready to plot on a Smith chart as polar coordinates.

Setting up a three-knob ATU is normally fun as you have to explore a bit to find the best VSWR dip. But if you try it with a phase meter working, it becomes a lot easier to do. The phase meter tells you which way to go.

R&S made an impedance monitor that compared the vector forwards and backwards sample voltages on a CRT. Linear voltages, no logging needed or wanted, but a scaling function needed. The CRT had a Smith chart directly on it. They called it the 'Diagraph'

The 'which direction do I go?' uncertainty also affects simple things like LCR bridges. HP made a neat little one with an added phase detector that lit one of two neon arrows above the main knob saying 'this way to the null'

You can have a lot of fun with these things.

I made my vector VSWR meter 30 years ago with a couple of sample AD640 loggers courtesy of ADI's rep. Their current versions are a LOT cheaper and far less current hungry there are also some decent phase detectors available as integrated parts.

One problem with phase detectors is that they will be somewhat iffy near the wrap-around point, so you have a blind spot that can be awkward to avoid.

Oh, and my big goof was that I built the whole thing into a monster ATU of a type which is completely unsuited to the HF antennae I can fit in at home. Ooops!

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now   Reply With Quote
Old 29th Feb 2020, 2:59 pm   #5
G0HZU_JMR
Octode
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,839
Default Re: Idea for a method of Z measurement.

A classic return loss bridge for amateur radio is as shown in the link below:

http://www.sv1bds.gr/homebrew/testme...turnlossbridge

I've shown a couple of the images from that website below that show a typical implementation in hardware that might work from 1MHz through the VHF band. It will require a terminated detector at the detector port and this could be a diode detector or a logamp or some form of 50 ohm analyser.

My old bridge was similar although I included a boost amplifier ahead of the diode detector. To minimise uncertainty from even order harmonics I used two diodes in the detector. I dug mine out today and it still works and it has 1-150MHz written on it so this must be the range it worked best over. It has been gathering dust for many years so I can't remember that much about how well it worked...

I'm not sure the RHO device will be quite the same inside. Is there a manual or a schematic for it?

I can show you how I would calibrate and quickly test my old RLB if that helps? If your RHO device is not quite the same then I'd recommend making a homebrew RLB using decent (small package) resistors and a decent balun.

The resistors in the images below look to be very big and may have a high self capacitance and some lead inductance. I think the balun could be better as well although it will be good enough for 1MHz to maybe 150MHz. The designer specs it to 1GHz which seems a tad optimistic.

I think you can buy a RLB ready made on ebay (from China) but I don't know how well they work. A lot depends on the layout, the components and the balun performance.

If there is no manual or schematic for the RHO device I can suggest a few tests to try and reverse engineer what is inside if that helps.
Attached Thumbnails
Click image for larger version

Name:	RETLOSSBRG1.jpg
Views:	55
Size:	80.2 KB
ID:	199896   Click image for larger version

Name:	RETLOSSBRG2.jpg
Views:	55
Size:	83.1 KB
ID:	199897  
__________________
Regards, Jeremy G0HZU
G0HZU_JMR is offline   Reply With Quote
Old 29th Feb 2020, 5:13 pm   #6
G0HZU_JMR
Octode
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,839
Default Re: Idea for a method of Z measurement.

I tried googling the RHO device and some of them do appear to be return loss bridges although they are marketed as VSWR bridges. They come with a N-type 50R reference load and several N type test loads with various VSWR.

eg 1.0:1, 1.2:1, 2.0:1, 3.0:1 and 4.0:1. Is yours like this?

If so it should be possible to calibrate it fairly easily. If you run it at a high detector drive level it may be a fairly linear detector and the calibration would only be required if you want to get the best from it.

The detector on mine is not very linear. I think the original calibration back in my youth was done using various metal film resistors as test loads at the test port. I then later revisited the calibration with an unterminated Hatfield 2105 step attenuator as the load device. 1dB on the attenuator would be equivalent to a 2 dB return loss, 3dB attenuation would be 6dB return loss with the far end of the attenuator is left unterminated.

Today I tried to calibrate it using a sig gen and the method in post #2 where I step the sig gen in 1dB steps. I have a very accurate sig gen here when stepped in 1dB steps so this was the quickest method.


The alternative is to use a step attenuator and if you can get hold of a healthy Hatfield 2105 attenuator that would be a good tool to use.

The alternative is to do it the way I did it decades ago at 10MHz using metal film resistors as the test loads. eg a 100R resistor has a 2:1 VSWR or 9.54dB return loss (and so on). This method is slow and a bit tedious but it would only take half an hour assuming you have an E12 or E24 range of resistors to use as test loads across a few ohms through maybe 1000R.
__________________
Regards, Jeremy G0HZU
G0HZU_JMR is offline   Reply With Quote
Old 29th Feb 2020, 5:41 pm   #7
G0HZU_JMR
Octode
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,839
Default Re: Idea for a method of Z measurement.

See below for an excel spreadsheet showing the calibration results and test results for my old RLB. Bear in mind that this was built in an evening probably 30 years or so ago using surplus parts.

The idea was that the diode detector port fed to my DVM and the cal point was set at 1.000V into an open circuit.

If the detector had been linear then the DVM would indicate the reflection coefficient directly but you can see that the column A (true reflection coefficient) does not agree with column D (DVM indicated reflection coefficient). This is because my detector was not linear and this is why I had to use a calibration chart to correct for the detector non-linearity.

One crude rule is that if you want to measure return loss within about 1dB then the directivity of your RLB needs to be 20dB better than the return loss of the test load. If you look at the test results in column G they agree with the column D quite well right down to about 22dB return loss. This is because my RLB has about 40dB directivity.

The errors get worse as you scan down and compare the grey coloured cells in columns D and G and I've colour coded them towards red as the errors mount up. However, this is still a very good return loss bridge in my opinion.

Your RHO device should be a bit better than this. If you can drive its detector into the linear region for most of the range it should be able to indicate the reflection coefficient fairly well down to about 0.1 or 0.15 without needing to calibrate it. You could just use an analogue meter with a scale of 0 to 1.0 FSD. You could then mark it with a secondary scale for return loss using a simple equation to tell you where the scale pips should be.
Attached Files
File Type: xlsx RLB_G0HZU.xlsx (16.0 KB, 15 views)
__________________
Regards, Jeremy G0HZU

Last edited by G0HZU_JMR; 29th Feb 2020 at 5:58 pm.
G0HZU_JMR is offline   Reply With Quote
Old 29th Feb 2020, 5:45 pm   #8
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 13,311
Default Re: Idea for a method of Z measurement.

You'll find a variety of these devices with a variety of names... Directional coupler, hybrid, return loss bridge.

Resistive techniques are closely like a wheatstone bridge and can go all the way down to DC if the detector is built in and floated. Others have transformers to isolate and give an RF output WRT ground.

Transformer and transmission line techniques can make low loss couplers which are good to high powers and which can also be used at low powers. Versions using waveguides and optical fibres get up to microwave and optical frequencies.

Just having a simple diode detector tells you how good a match is either as a VSWR or return loss figure. Useful for checking, but they can't discriminate too high resistance from too low, nor inductive or capacitive effects. They tell you how much you missed the bull's eye by, but fail to tell you in which direction.

The simple diode detector on any variety of coupler will let you assess RF impedances in terms of match quality, which is what you said in the original post. there are, however other systems which use the phase information as well. These can actually measure impedances at radio frequencies and tell you whether things look capacitive, inductive, big-R or small-R or combinations of the above. These tend to be much more complex (bad pun) machines and more costly.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now   Reply With Quote
Old 29th Feb 2020, 8:50 pm   #9
Skywave
Dekatron
 
Skywave's Avatar
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 6,726
Thumbs up Re: Idea for a method of Z measurement.

Gentlemen: thanks for your posts; useful and informative. A lot to digest - but that's just fine!

Aside.
Now with all due respects to Paul Stenning and the mod. team, I was a bit doubtful that I would receive any responses to my OP, since - in my opinion - my post is a 'bit on the fringe side' of topics for a vintage radio forum. But I suspected that if I did receive any such replies, it would be from you two guys!

Quote:
Originally Posted by G0HZU_JMR View Post
. . . a step attenuator and if you can get hold of a healthy Hatfield 2105 attenuator that would be a good tool to use.
I hadn't thought of that. But I do have such an item - and an HP 335D switched attenuator as well. So, time to make some more measurements . . . see further down . . .

Quote:
Originally Posted by G0HZU_JMR View Post
. . . do it the way I did it decades ago at 10MHz using metal film resistors as the test loads. e.g. a 100R resistor has a 2:1 VSWR or 9.54dB return loss (and so on). This method is slow and a bit tedious but it would only take half an hour assuming you have an E12 or E24 range of resistors to use as test loads across a few ohms through maybe 1000R.
Which is exactly what I did between my OP and now, and plotted a graph of Vout (d.c.) against various mis-match loads (40Ω to 65Ω). Energizing signal was my HP 8640B: about 700 mV r.m.s. I had previously determined that the linear dynamic range of the 'RHO-Tector' was from about 500 mV to at least 1000 mV (8640B voltmeter). The 'RHO-Tector' claims a B/W from 500 kHz to 2.5 GHz at 0.5 watt. (Is this the device max. internal dissipation or max. power throughput?)

I repeated same tests at different freqs. (same drive level): 20, 50 and 80 MHz. For loads < 50Ω, responses were same at all freqs., but for loads > 50Ω, there was an increasing reduction in the V d.c. out as freq. and magnitude of mismatch was increased (140 mV as opposed to 150 mV - which is only a 7% error, and at high mismatched loads too). I suspect that could have been due using metal oxide Rs and / or 'invisible' impedances at the BNC sockets where the mismatch loads were soldered.

I also found - when plotting the graph Vout vs. load R ( and consequent RC & RL) - a few points which were well away from the implied curve (which looks approx. parabolic). In one case, replacing the load R by another exactly same, made all the difference and produced a 'believable' result! But not so in two other cases: so I ignored those 'erroneous' points when I sketched in the resultant curve.

Last measurement was same as above, but over a smaller range of load Rs.: 46Ω to 54Ω. That range is probably appropriate for what I hope to use this RHO-Tector for. Vout d.c. was 1 mV max., so some d.c. amplification will be required.

Having said all that, above results were with 700 mV drive, which is almost certain to be far too high for things I hope to be using this 'RHO' device with. Overall then, I need to do a bit more experimentation & development with this idea, but I do feel that there are encouraging signs so far . . . .

Al.
__________________
Never act on your first idea. Like solving a crossword clue, a better idea arrives tomorrow.

Last edited by Skywave; 29th Feb 2020 at 8:55 pm.
Skywave is offline   Reply With Quote
Old 29th Feb 2020, 10:11 pm   #10
G0HZU_JMR
Octode
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,839
Default Re: Idea for a method of Z measurement.

If it helps, I put together a simulation of a classic return loss bridge and stuck a video up on youtube. Sadly there is no sound, I have no microphone here but you can see how the various RF waveforms change within the return loss bridge as the load impedance is changed. The line stretcher allows the bridge to be presented with all impedances that fall on a given VSWR circle and you can see how the amplitude and phase changes for the various RF waveforms within the bridge.


https://www.youtube.com/watch?v=5xHp...ature=youtu.be

I presented it with a short circuit to start with, then an open circuit and then a 100 ohm load for a 2:1 VSWR. I then 'stretched' the line to rotate the impedance around the full 2:1 VSWR circle on the smith chart. I also tested at 3:1 VSWR, 10:1 VSWR and 1.1:1 VSWR and rotated around the smith chart in each case.

I set the drive level such that the green sinewave at the detector port had a Vpk of 1.0V with a reflection coefficient of 1. So this Vpk should be the same as the reading for the Reflection Coefficient chart below it.

There are also charts for VSWR and return loss and hopefully it is all OK. I did it in a bit of a hurry so I may have missed something somewhere.
__________________
Regards, Jeremy G0HZU
G0HZU_JMR is offline   Reply With Quote
Old 2nd Mar 2020, 6:02 pm   #11
Skywave
Dekatron
 
Skywave's Avatar
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 6,726
Default Re: Idea for a method of Z measurement.

Further investigations of this Telonic 'RHO-Tector' have now led me to the conclusion that it will be unsuitable for my intended applications, to wit, the determination of the degree of the impedance match / mis-match of the input Z of low-power amplifiers, etc., to a 50 Ω generating source.

That is because not only is its d.c. output level non-linear below about 500 mV of R.F. input - a level far in excess of the above-stated anticipated application - but also that for R.F. inputs in the region of 10 → 100 mV, the d.c level out is so small as to be totally undetectable.

My research (incl. reading stuff on the 'Net) leads me to believe that what is needed is a D.C. for low-power applications, which will probably have a coupling factor of only a few dB.

Methinks the 'D-I-Y' route is required here, which, for me, will be daunting challenge!

A.
__________________
Never act on your first idea. Like solving a crossword clue, a better idea arrives tomorrow.
Skywave is offline   Reply With Quote
Old 2nd Mar 2020, 7:24 pm   #12
G0HZU_JMR
Octode
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,839
Default Re: Idea for a method of Z measurement.

The new kid on the block is of course the little 35 nanovna but if you want to experiment with a sig gen driving a return loss bridge then you could look on ebay.

Lots of people in China are selling the same PCB based 3000MHz return loss bridge for about 7 on ebay. I seriously doubt it will work well to 3000MHz but you could make a copy of their circuit using a similar balun if you want to make it yourself.

You could fit a 50 ohm terminated AD8307 logamp as the detector and this will report the return loss with a scaling of 25mV/dB. However, the AD8307 will only work up to about 500MHz and it will show a reasonably flat response to maybe 100MHz of so. It will work down to RF levels of -70dBm so there would be no problems with sensitivity and it would be easy to calibrate on an analogue meter scale because the response of the logamp is 25mV/dB.
The quick and dirty alternative would be to use a 50 ohm terminated scope as the detector. However, this would soon become tiresome I think.
__________________
Regards, Jeremy G0HZU
G0HZU_JMR is offline   Reply With Quote
Old 3rd Mar 2020, 12:10 am   #13
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 13,311
Default Re: Idea for a method of Z measurement.

I don't recall you mentioning what frequency range you wanted.

Homebrewing this sort of thing isn't daunting at all .... It's fun!

It's amazing what you can do that you didn't know you could.

If you want to move a bit of power, without significant loss, then the two transformer hybrid (it's like a bridge, using the source, load and the derector terminations as the arms even though they aren't obviously wired ad a bridge, they work as one.

Wes Heyward put one in one of his books... Experimental Methods, I think

I put one in Sprat isue 61 with a couple of diode detectors and meters, but the hybrid can be used alone. Covers topband to about 50 MHz with good accuracy though people say it's good enough to 2m. The circuit's on the web in various places if you google Stockton Wattmeter. No I didn't choose that name (it's the last one I'd have) Dick Pascoe (Kanga) did that as a play on PW's penchant for naming things after towns.

The day job once included designing some hybrids for measuring balanced loads in the 135 and 600 Ohm region. They went to telecomms PTTs and places like Bell labs. Had to get those dead on, and beat the opposition's bandwidth and null depth ;-)

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now   Reply With Quote
Old 4th Mar 2020, 11:12 am   #14
Skywave
Dekatron
 
Skywave's Avatar
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 6,726
Arrow Re: Idea for a method of Z measurement.

Frequency range of interest is approx. 1 MHz to 100 MHz.

However, since my last post, the computer system here has incurred a strange problem, rendering backups-by-cloning defective. Fixing this is proving to be very difficult - but must take priority. So, until that problem is resolved, any further work in this 'directional coupler' topic will have to wait. My thanks to everyone who has contributed to this thread so far.

To repeat a familiar phrase "I'll be back"!

TTFN,
A.
__________________
Never act on your first idea. Like solving a crossword clue, a better idea arrives tomorrow.
Skywave is offline   Reply With Quote
Old 4th Mar 2020, 7:00 pm   #15
John KC0G
Pentode
 
Join Date: Mar 2009
Location: Minneapolis, Minnesota, USA.
Posts: 133
Default Re: Idea for a method of Z measurement.

Post #4 from David makes several references to phase meters. Clearly they can be very useful. But then why does one see so few references to, and articles about, them?

I recall their being mention of them by Pappenfus et al in the book "Single Sideband Principles and Circuits", McGraw Hill, ca. 1964. This is one of the excellent books written by Collins staff. Collins used phase meters in some of their ATU's. There was a mention in Technical Topics in the August 1989 issue of Radcom. And G3YNH has included them in his discussions on his web site at http://g3ynh.info and his section on the G3GFC M50 Match meter at http://g3ynh.info/zdocs/m50/index.html

Does anybody know of good articles on phase meters for HF use?

Thanks and 73

John
John KC0G is offline   Reply With Quote
Old 5th Mar 2020, 12:04 am   #16
Radio Wrangler
Dekatron
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 13,311
Default Re: Idea for a method of Z measurement.

Quote:
Originally Posted by John KC0G View Post
Post #4 from David makes several references to phase meters. Clearly they can be very useful. But then why does one see so few references to, and articles about, them?
John
Well they're more difficult than VSWR metering

Most people are a bit afraid of phase like people who may be happy enough with linear measurements and algebra get phased by trigonometry (deliberate, sorry, but irresistable)

Many HF rigs with auto ATUs in them have a phase meter. They need it to know which way to drive the servo motors. It isn't brought out to the front panel meter, though.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is online now   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 10:22 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 - 2020, vBulletin Solutions, Inc.
Copyright ©2002 - 2020, Paul Stenning.