3rd Nov 2022, 8:02 pm | #61 | |
Heptode
Join Date: Apr 2003
Location: Cornwall, UK.
Posts: 989
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Re: 2nd November - UK CB anniversary
Quote:
My rig at the time was the basic Audioline 340 with the Uniden chassis, and in comparison to the Fidelity was like night & day. They were nicknamed ‘bleed over merchants’ down this way.... SimonT.
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The honesty of imperfection.......... Last edited by thermionic; 3rd Nov 2022 at 8:02 pm. Reason: Quote fixed. |
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3rd Nov 2022, 8:14 pm | #62 | |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: 2nd November - UK CB anniversary
Quote:
Thanks for going out and braving the conditions to test that little Fidelity, I was genuinely interested to know whether it really was as bad as its reputation would have it - I saw a few back in the day but they only crossed my bench as repairs and I never got to spend time using one so like you, I have often wondered whether they were really so bad. It seems like the receiver's openness to all and sundry is genuinely a strike against it and as you say it would have been intolerable back in the day, and I'm afraid it might still prove so in this day and age under summer sporadic 'E' conditions where you would most likely get hammered by SSB signals intruding from further down the band. What will you do with it now, I wonder? |
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4th Nov 2022, 5:58 pm | #63 |
Nonode
Join Date: Apr 2012
Location: Worcestershire, UK.
Posts: 2,052
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Re: 2nd November - UK CB anniversary
"As we all know from watching Smokey and the Bandit / Dukes of Hazzard, any vehicle with a boot mounted aerial, ideally a Firestik(TM), can clear a gap at least ten times its own length and land miraculously unharmed at the other side. You could have saved yourself a bit of time there."
Brilliant! Made my day, that one ... Guy
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"What a depressingly stupid machine." [Marvin: HHGTTG] |
4th Nov 2022, 6:10 pm | #64 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: 2nd November - UK CB anniversary
I'm thinking that maybe Techman can donate his Fidelity to a museum. In most cases that would be a sure-fire way to make sure that nobody will ever get the opportunity to use it again.
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4th Nov 2022, 6:16 pm | #65 |
Nonode
Join Date: Oct 2010
Location: Gloucester, Glos. UK.
Posts: 2,150
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Re: 2nd November - UK CB anniversary
Did anyone ever have a DNT M40?
Ive got one and tbh it sounds even worse than the Fidelity !!! Its got to be the worse CB ive ever owned for bleed over etc etc.
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Oh I've had that for years dear!! |
4th Nov 2022, 6:27 pm | #66 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: 2nd November - UK CB anniversary
I think I may have one in my loft which is on 10m - already that way when I got it. I didn't admire them much when in their original CB radio guise. I've just had to look at an online image of one to remind myself what they look like and it's interesting to see they have the less common green channel LEDs - that can be a spare-in-waiting in case I ever need one for a more worthwhile radio like a Rotel.
There is actually one good reason to buy up the really terrible, unpopular radios whenever they come up for next to nothing - no matter how nasty they are, they will still have an original RF driver and output transistor, hopefully both still working. They are worth buying up just to get those now. |
4th Nov 2022, 8:51 pm | #67 |
Tetrode
Join Date: Mar 2019
Location: Grantham, Lincolnshire, UK.
Posts: 79
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Re: 2nd November - UK CB anniversary
The weather was pretty nasty here on evening on the 2nd, otherwise I was intending to go out mobile with my only CB set I have, an old school Harvard 402MPA and Siro ML145. Don't know if I would have had any contacts, but would have been good to hear the channels alive with chatter again.
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4th Nov 2022, 9:04 pm | #68 | |
Dekatron
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
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Re: 2nd November - UK CB anniversary
Quote:
I think the radio was fitted with a crystal filter at the first IF and there may have been other changes. I can remember the CB magazines at the time rated the Supertuned DNT M40 as one of the best CBs they had tested.
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Regards, Jeremy G0HZU |
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4th Nov 2022, 9:24 pm | #69 | |
Dekatron
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
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Re: 2nd November - UK CB anniversary
Quote:
For example, the budget Harrier CB model had the smaller ceramic filter. The more expensive Harrier CBX had the larger ceramic filter. I think it was the same for the cheaper Rotels vs the top of the range Rotel RVC240. The same again for the budget York 861 vs the more expensive York 863. All these radios used the 134 chassis but only the expensive models had the larger 455kHz ceramic filter. I think the same applies for the extra IF transformer. Only the top end models had the extra IF transformer.
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Regards, Jeremy G0HZU |
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4th Nov 2022, 9:44 pm | #70 |
Pentode
Join Date: Dec 2017
Location: Huddersfield, West Yorkshire, UK.
Posts: 193
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Re: 2nd November - UK CB anniversary
Damn! All the cb's I have and I forgot
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5th Nov 2022, 11:55 am | #71 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: 2nd November - UK CB anniversary
...As indeed you did last year
https://vintage-radio.net/forum/show...1&postcount=98 We're going to have to club together and buy you a calendar! In truth, it was a bit muted this year because the awful weather discouraged all but the most lion-hearted of us from venturing out onto high spots. The following two evenings of course were fine and dry. |
5th Nov 2022, 5:44 pm | #72 |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 5,000
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Re: 2nd November - UK CB anniversary
Well perhaps not a lot. However, having put it away on a shelf with other radios I decided to fetch it out again and have another look inside and do some comparisons with the other scrap chassis that I've got and the circuit diagram that you posted a link to.
I thought that I'd already got a copy of an original Fidelity 1000 circuit diagram somewhere, but I couldn't find it - perhaps it's a hard copy (photocopy) that's filed away somewhere, but never mind. There's a full service manual for these out there somewhere, I've seen it, but as far as I know it's not available anywhere on the 'net, that I can find. So looking at the re-drawn diagram that you previously linked to (hats off to Colin Hinson for taking time out to do it) it was interesting to note a few things, particularly in the side notes. I printed it off, but needed a magnifying glass to see them, so better enlarged to 400% on the pdf. He mentions replacing the first IF 10.7MHz ceramic filter with a better crystal type. I've heard this mentioned before and had been thinking about this already, so just wondering what bits of scrap chassis I can pinch one off. Talking to someone last night who I get old gear off when he's having a sort out, he says he's going to look to see what he's got in the shed sometime in the next couple of weeks, that's if I don't come across something before then - we'll see, it's not that important, just an interesting case of seeing if that's the main problem, and I suspect that it may very well might be. I notice that the radio itself is stamped as 13.2 volts on the rear of the chassis and interestingly the wattage output when running on exactly that voltage is 4.5 watts, so will be slightly more on 13.8 to 14.4 when in a 'running' mobile - it would have been slightly less on a non-charging car battery the other night at around 12 volts. Someone's going to suggest that not all of those watts are on the frequency they're supposed to be on, well I've not specifically checked, but it was certainly performing on output equally as well as the Radiomobile which has the Cybernet 134 chassis inside, so I don't think there's anything to worry about in that respect. You can't fault the audio output quality on this set as far as I can tell (it would be interesting to hear someone else on it to get a proper idea), but it's when someone asks how a radio sounds over the air and so many times you hear "well I can understand what you're saying, so it's alright", you pretty much know that what they really mean is that it sounds rough and they're just being kind - there's been nothing like that with this radio so far...and you can't say that for some of the radios out there. I think it was an ideal radio to try to work with for the anniversary, seeing as many on a tight budget would have purchased this model back in '81 and onwards - I don't know whether they were available on the actual first day of legalisation or in the months that followed, but I understand that they were near on seventy quid to buy when new, perhaps compared to a hundred or so for a Rotel. Anyone who's been looking lately will have spotted that someone has found some 'apparently' new old stock of these radios and if you were a 'serious' collector then it's probably a 'never-to-be-repeated' opportunity to get one, regardless of what many would say is a rather optimistic asking price. It looks like there are only two of these collectors out there so far and the remaining sets are struggling to sell. I actually wonder whether they really are brand new in the box never used or are in fact manufacturers returns or similar, as there's different felt pen markings on the boxes and it's stated that they've been opened to just check what was inside (or similar) - who knows, but they certainly look brand new. Was the Radiomobile a good choice for the anniversary? I don't know, it worked well enough and again, I don't know if it was available for purchase on exactly the first day in 1981. However, it is a good design for a genuine mobile (in car while driving) radio. It doesn't have an 'S' meter, which you wouldn't want to be looking at while driving - the green 'dots' are all you need as a quick indication of received signal. The microphone input is on the front panel - ideal for when fitted in a vehicle. Channel 9 emergency push button would have been good thinking at the time, but irrelevant now - and probably even back then. Other knobs such as RF and mic gain are maybe questionable on a mobile rig, but all in all still a very good mobile rig...just not ideal for static mobile on the night, as you really need a proper signal meter to answer all the signal report questions truthfully - lucky I had the Fidelity for this, although some when operating the Radiomobile, I just told them that I'd got four lights and how many they were lighting and make of that what you will and if they really wanted to know then I'd switch over to the Fidelity. In general the night was a bit of a flop, but it was a bit of fun and it tested a couple of old rigs out in the wild, particularly the Fidelity and it was good to natter to several folk who I already know anyway. It's surprising how many didn't know about the event, even the locals in my area didn't know until I made the effort to go on and tell them a day of so beforehand. A lot of these operators aren't 'forum' type people, so don't read the sort of stuff that I and others might happen to spot while browsing. There was absolutely no doubt that the biggest killer was the weather. The serious folk who would have been 'up-to-speed' on what was happening and gone out onto a high spot mostly decided to give it a miss - as I was nearly going to do. I also think that last year was a bit special and I think that it's unlikely to ever be repeated. I think it's time to actually show the terrible Fidelity, so below are pictures, the first being the radio, the next two being the innards and the last two are both sides of the scrap Gecol chassis for comparison. The output of the Fidelity on low power is only 0.2 watts. I thought there would be a pre-set with perhaps a dirty track, but there isn't and low power is achieved by opening the switch across a 39 ohm resistor - the resistor is a 'quality' wire wound (different on the Gecol chassis) and measures exactly as it should. The chassis are made by 'Great' (not so great). I don't know anything about 'Great' and haven't researched them (yet), but I suspect that the circuit is derived from some much earlier AM only design. I think it's C129 that's omitted on the board, but on the Fidelity it's actually written in hand written style font on this version, but normal font print on the Gecol scrap chassis board - interesting oddities. Pictures below - note the lack of that screening plate on the print side of the RF output stage on the Fidelity compared to the scrap Gecol version - it doesn't look like its ever had one fitted, and why would it need one anyway with it having full metal screening from the case just a few extra mm away? Perhaps there's some extra stray capacitance caused by that screen being so close to the print that prevents the RF output from being tuned to its full potential on the models that have it fitted...one wonders... Last edited by Techman; 5th Nov 2022 at 6:01 pm. |
5th Nov 2022, 10:51 pm | #73 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: 2nd November - UK CB anniversary
It's certainly in much nicer condition than my beloved 5-Star so I can understand why you took a chance on it - if it had been a Fidelity 1000 and in poor condition I doubt that you would have gone for it.
I may have a 3-terminal 10.7MHz crystal filter here which I intended to try or possibly even did try in my Tristar 777 not long after I first got it - didn't work well for whatever reason, but I think I still have the filter in my bits box. My RF design knowledge is very poor but I would imagine ceramic filters and crystal filters aren't a drop in replacement for each other, they probably have different impedances which need to be matched when one is replaced with the other. There was at least one 'active' crystal filter upgrade available from various 'rig mod' sellers, a little PCB with a crystal filter and a buffer / impedance matching stage. Whether the Radiomobile was available on day one or not, radios using the same chassis definitely were so I would say that it is representative of one type of radio which was in common use from the first day. |
6th Nov 2022, 10:48 am | #74 | |
Pentode
Join Date: Dec 2017
Location: Huddersfield, West Yorkshire, UK.
Posts: 193
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Re: 2nd November - UK CB anniversary
Quote:
At home I mostly have my sdr play rsp2 on my aerials (cb and 2/70) and monitor the terrible intermittent interference (I suspect close by grow lights ) +10 to +30 db with a WIDE frequency spread |
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6th Nov 2022, 11:08 am | #75 | |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: 2nd November - UK CB anniversary
Quoting myself:
Quote:
http://www.spectrumcomms.co.uk/CB_Kits.htm |
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6th Nov 2022, 6:18 pm | #76 |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 5,000
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Re: 2nd November - UK CB anniversary
Yes, of course, Spectrum.
I was going to phone up Tony regarding ordering some other bits and pieces earlier this year (or was it last year?) and before I got round to doing it I heard that his wife had recently passed away and that he had put the business temporarily on hold, so decided to leave things for the time being. I could only imagine how he must have been feeling under such dreadful circumstances. I'd forgotten all about this until just now, so I think this will be the way to go. When we think of ceramic and crystal in terms of audio frequency and record player pickup cartridges, it's always regarded as ceramic being better - they're certainly more long lasting. Ceramic cartridges tend to have a 'smoother' response in record players than crystal cartridges do, but this is actually a possible indication that at the frequencies and use that we're talking about here, ceramic is definitely not so good. There's no impendence matching problem at audio frequency, with them both being matched to 1 - 2 Meg, possibly very different at much higher frequencies and sharp filter usage that we're talking about here. |
6th Nov 2022, 6:28 pm | #77 |
Dekatron
Join Date: Nov 2009
Location: Lincolnshire, UK.
Posts: 5,000
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Re: 2nd November - UK CB anniversary
They're maybe all using another channel much further up the band rather than the old 19. Virtually none of the sensible folk monitor 19 anymore, well certainly not in my area, anyway.
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7th Nov 2022, 12:24 am | #78 |
Dekatron
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
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Re: 2nd November - UK CB anniversary
I think I've still got some of the 10.7MHz crystal filters here. Back in the day, there was the choice of 7.5kHz bandwidth and 15kHz bandwidth filters. Most people wanted the 7.5kHz BW filters. Some people used two 15kHz bandwidth filters in series to try and get extra stopband performance.
At the time these became available I was still a young student and didn't really know how to impedance match these filters as I didn't have the test gear back then. All I can say is that I never fitted any of these crystal filters to any of my radios as they usually introduced some slight distortion to the received audio. This may have been due to group delay effects and/or mismatch ripple due to incorrect impedance matching. The 7.5kHz BW version was the worst in this respect. I think the wisest thing to do back then was to buy and use one of the better CBs for 'bleedover' and that's what I did. However, plenty of CBers were desperate to have these filters fitted and nobody complained of distortion even though I could usually hear it. I can remember using the Fidelity 1000 and the Cheiza equivalent model. In a busy town they were almost useless due to the wide-open receiver. Note that I think these radios also used a basic ratio detector rather than the classic limiter and quadrature detector found in other UK FM CBs.
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Regards, Jeremy G0HZU |
7th Nov 2022, 12:34 am | #79 |
Dekatron
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,575
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Re: 2nd November - UK CB anniversary
I happened to email Tony with an order for some small parts a while back and it seemed to be taking slightly longer than it ought to, allowing for any reasonable circumstances. I queried the delay, only to find that in the interval between my placing the order and my following up on the seemingly overdue order, Tony's wife had suddenly passed away. You can imagine how I felt about having bothered him for the sake of a delayed order for a few low value ceramic caps and trimmer capacitors. Worst. Timing. Ever.
The wording of the description for Tony's 'active' filter really makes me wonder if these were the exact radios he had in mind when devising this mod. Although the page does state at the top that the prices are out of date I think I would be interested enough to risk whatever the current small outlay may be to try it out, although 'small' in this case may be nearly as much as you paid for the radio. Regarding the filters, apart from the possibility that the termination impedances may be different, there is also the likelihood that a filter which really effective at removing everything outside its passband also introduces a bit more attenuation at the 'wanted' frequency than a less effective filter would, so that is the reason (or one of the reasons) why the Spectrum Comms filter PCB also includes an active buffer stage, to compensate for insertion loss. Edit, crossed with Jeremy:- In the case of the Tristar 777 I mentioned that I had tried to fit a 3-wire crystal filter to, if memory serves me correctly the Cybernet 125 chassis did not even have a 10.7MHz ceramic filter to replace with a crystal filter - hence its terrible receiver performance in urban environments - so I just removed the low value coupling capacitor (C120, 2pF) in the Mixer / 10.7MHz IF stage and inserted the filter across that capacitor's position (with its centre / earth terminal taken to GND) and I didn't like the way it sounded. I soon reverted it back to as-built. I had no idea then (and not much idea now) of how to do the job properly. This was decades ago, by the way. Last edited by SiriusHardware; 7th Nov 2022 at 12:46 am. |
7th Nov 2022, 12:52 am | #80 |
Banned
Join Date: Jan 2009
Location: Littlehampton, West Sussex, UK.
Posts: 142
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Re: 2nd November - UK CB anniversary
Gawd!!....The 'Fidelty' 1000 (As I recalled someone call them on the air) was truly dreadful in many ways! Sold under a cavalcade of different names, it had the worst front end ever we all used to agree on!! Strange 'Bleedover' & terrible selectivity made these sets a laughing stock! Interesting then that there are SO many left, some in great condition too! My fave set for simplicity was the Maxcom range! The 4E being the most popular - I favoured the the tiny 21E as it was so tiny with the leds instead of an analogue meter! Would love to find a nice one again!
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