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 > Specific Vintage Equipment > Vintage Amateur and Military Radio

Notices

Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

Reply
 
Thread Tools
Old 27th Nov 2018, 11:27 am   #41
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 7,668
Default Re: 10M FM - any activity these days?

Quote:
Originally Posted by GSBX1220 View Post
Some photos of my DNT 10m conversion. No add on boards or any obvious mods on this one. Not sure how it was done. I bought it for a couple of quid many years ago at a rally.
The DNT (and the similarly-synthesized Icom 1050) could be converted by linking a few pins on the PCB and adding a pull-up resistor. From memory it only thehn had 30 channels - unless you added a SPCO switch whereupon you then got 60 channels.
G6Tanuki is online now   Reply With Quote
Old 27th Nov 2018, 1:36 pm   #42
GSBX1220
Tetrode
 
Join Date: Jun 2018
Location: Glasgow, Scotland,UK.
Posts: 92
Default Re: 10M FM - any activity these days?

After I posted that, i done a quick google. The DNT uses a motorola PLL and changing the PLL crystal & quick re alignment you are good to go. Mine has 40 channels. No switch.

Quite a good wee set on 10
__________________
Richard
GM7KIM
GSBX1220 is offline   Reply With Quote
Old 27th Nov 2018, 2:23 pm   #43
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 3,006
Default Re: 10M FM - any activity these days?

I take it there must be at least one more crystal in addition to the 10.240Mhz reference crystal, i.e, the 'loop mixer' crystal. A refinement would be to insert an eprom between the channel switch and PLL, programmed such that either:

(Repeater shift = off)
-All channel switch codes are passed through unaltered

or

(Repeater shift = on)
-Channel codes 31-40 are shifted down by 100Khz / 10 channels in TX
-Channel codes 21-30 are shifted up by 100Khz / 10 channels in TX.

(This assumes that channel 21=29.500Mhz and channel 40 = 29.690MHz).

Unfortunately there is only one operational 'classic' 10FM repeater in the UK that I know of, near Northampton. Another looks to be coming online soon near Norwich. Both are likely to prefer CTCSS for access.
SiriusHardware is online now   Reply With Quote
Old 27th Nov 2018, 3:16 pm   #44
Steve G4WCS
Hexode
 
Steve G4WCS's Avatar
 
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 253
Default Re: 10M FM - any activity these days?

with thanks to Dave757. DNT manual and conversion details attached
Attached Files
File Type: pdf DNT M40.pdf (433.4 KB, 34 views)
Steve G4WCS is offline   Reply With Quote
Old 27th Nov 2018, 4:33 pm   #45
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 3,006
Default Re: 10M FM - any activity these days?

A lovely bit of info, thanks to Dave for making it available and Steve for posting it here.
SiriusHardware is online now   Reply With Quote
Old 27th Nov 2018, 7:36 pm   #46
rambo1152
Octode
 
rambo1152's Avatar
 
Join Date: May 2010
Location: Manchester, UK.
Posts: 1,436
Default Re: 10M FM - any activity these days?

I haven't managed to track down the Bury Radio Society article, but I can tell you there were two articles in their "Feedback" newsletters
March 1983 & May 1984
Information came from this New York state club's recent publication Pages 9-13

http://home.computer.net/~pcara/docs/pcud1118.pdf
__________________
--
Graham.
G3ZVT
rambo1152 is online now   Reply With Quote
Old 27th Nov 2018, 8:14 pm   #47
Jon_G4MDC
Heptode
 
Jon_G4MDC's Avatar
 
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 685
Default Re: 10M FM - any activity these days?

Si5351a RX VFO was patched into my 10m FM10D on Sunday.
Colpitts oscillator robbed of feedback to use as buffer.

Some issue with drive levels, not nearly as much Ic as when working as normal crystal oscillator. Si5351a is nominal 50 Ohms out with variable current drive levels set by software bits.

Making FM10 Cambridge Oscillator more like Common Emitter Amplifier and by stepping up the drive by 4:1 transformer then the buffer (as it was oscillator VT3)
Ic hit near normal levels.

It can hear things in the right places but there is a birdie at around 29.7MHz. It tunes a signal which is not there. Don't know the source of that as yet.

Last edited by Jon_G4MDC; 27th Nov 2018 at 8:41 pm.
Jon_G4MDC is offline   Reply With Quote
Old 27th Nov 2018, 8:22 pm   #48
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 7,668
Default Re: 10M FM - any activity these days?

I vaguely remember that some Pye gear had the option of specifying an alternative second-conversion oscillator frequency when a harmonic would have fallen on - or close to - an intended working-frequency.
G6Tanuki is online now   Reply With Quote
Old 27th Nov 2018, 8:34 pm   #49
Jon_G4MDC
Heptode
 
Jon_G4MDC's Avatar
 
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 685
Default Re: 10M FM - any activity these days?

Yes it did - good recall.
This one is strange altogether. 6MHz first IF. Not recalling original build frequency no idea whether it will be 6.455MHz or else 5.545MHz as 2nd LO.
It is hidden under a cover plate - so far not removed. I calculated for them both but so far I can't find the hits to blame.

Last edited by Jon_G4MDC; 27th Nov 2018 at 8:43 pm.
Jon_G4MDC is offline   Reply With Quote
Old 28th Nov 2018, 8:21 am   #50
Steve G4WCS
Hexode
 
Steve G4WCS's Avatar
 
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 253
Default Re: 10M FM - any activity these days?

Quote:
Originally Posted by rambo1152 View Post
I haven't managed to track down the Bury Radio Society article, but I can tell you there were two articles in their "Feedback" newsletters
March 1983 & May 1984
Information came from this New York state club's recent publication Pages 9-13

http://home.computer.net/~pcara/docs/pcud1118.pdf
awesome, yes it was that special edition feedback article I had
Steve G4WCS is offline   Reply With Quote
Old 28th Nov 2018, 12:37 pm   #51
Steve G4WCS
Hexode
 
Steve G4WCS's Avatar
 
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 253
Default Re: 10M FM - any activity these days?

spent an enjoyable morning at work browsing short wave magazine

https://www.americanradiohistory.com/Short_Wave_UK.htm

found the following pertinent articles

Feb 83 simple conversion method

April 83 repeater shift

Jun 83 Further mods ICB1050

Mar 84 how to convert "unconvertible" rigs

Nov 84 ICB1050 conversion update, LCL-2740 display mod

Dec 84 ICB1050 channel scanner
Steve G4WCS is offline   Reply With Quote
Old 28th Nov 2018, 6:32 pm   #52
Jon_G4MDC
Heptode
 
Jon_G4MDC's Avatar
 
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 685
Default Re: 10M FM - any activity these days?

I like your work!
I must be doing it wrong somewhere
Jon_G4MDC is offline   Reply With Quote
Old 29th Nov 2018, 11:32 am   #53
Steve G4WCS
Hexode
 
Steve G4WCS's Avatar
 
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 253
Default Re: 10M FM - any activity these days?

Not really. work for a large company between contracts and havent had much to do in spells this year.
Its hard work getting up at this time of year to sit and try and look busy, when I could be gainfully employed at home doing real stuff. now if I could bring radios and a soldering iron in...
Steve G4WCS is offline   Reply With Quote
Old 9th Dec 2018, 11:21 pm   #54
Steve G4WCS
Hexode
 
Steve G4WCS's Avatar
 
Join Date: Sep 2004
Location: Preston, Lancashire, UK.
Posts: 253
Default Re: 10M FM - any activity these days?

Sorry if I outbid anyone on here but had to have it 😁
Attached Thumbnails
Click image for larger version

Name:	116F70F3-FA46-474B-95D0-694E4106B21D.jpg
Views:	79
Size:	23.6 KB
ID:	174289  
Steve G4WCS is offline   Reply With Quote
Old 9th Dec 2018, 11:35 pm   #55
SiriusHardware
Dekatron
 
Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 3,006
Default Re: 10M FM - any activity these days?

Looks in beautiful condition, so much so that I would be reluctant to modify it at all. Is that what you intend to do with it?
SiriusHardware is online now   Reply With Quote
Old 10th Dec 2018, 10:26 pm   #56
Jon_G4MDC
Heptode
 
Jon_G4MDC's Avatar
 
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 685
Default Re: 10M FM - any activity these days?

Time machine!
That has to be a shelf queen surely?
(Borrowed that from the pressure lamp guys - if it looks really nice but it might just blow up in actual use then that is it's destiny)

Except of course you have to know whether or not it works...
Jon_G4MDC is offline   Reply With Quote
Old 11th Dec 2018, 12:45 am   #57
G0HZU_JMR
Octode
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,694
Default Re: 10M FM - any activity these days?

Somewhere in the loft I've got a mint condition Uniden 2830 multimode CB/10m radio and this covers 10FM. I bought it when CB had died and prices were still low and couldn't resist buying it. The accessories were still sealed in plastic and unused and the radio looks new, and I mean squeaky, shiny new with no marks anywhere. It's an early model with a low serial number and still had the dealer's original anti tamper seals on it and so it hasn't been converted to cover the CB bands. I'm not sure what it's worth nowadays.

Being the early model it has a wide ceramic 10.7MHz IF filter followed by an MC3357 FM/IF chip and it is probably the worst 'CB' I've ever used in terms of signal handling. I recall that I measured the input IP3 to be about -55dBm on FM. I guess this wouldn't matter much on 10FM these days unless there was strong sporadic E propagation. It's a very pretty radio but it is technically very poor in many ways. I don't think Uniden knew how to design multimode radios properly but then again I don't think Cybernet did either.

The Icom 1050 CB was another radio that suffered badly with overload. Probably not quite as bad as the early Uniden 2830 model but I'd recommend putting a decent 10.7MHz crystal filter in it ahead of the 3357 chip.
__________________
Regards, Jeremy G0HZU
G0HZU_JMR is offline   Reply With Quote
Old 11th Dec 2018, 9:16 pm   #58
Jon_G4MDC
Heptode
 
Jon_G4MDC's Avatar
 
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 685
Default Re: 10M FM - any activity these days?

I forget what I did to my dear old Icom 1050. 23 from the Tottenham Court Road a few weeks after 27/81 day. I drove there to buy it cash. I even managed to find a parking space. Today it would attract a 50% surcharge just for doing that.

It still hangs under my bench shelf but it has not had much use for many a year.
Squelch and S meter circuit was rubbish but easily sorted.
Later the 1st JFET mixer was replaced by dual gate.

It has some better 10.7MHz filter but for the life of me i don't know what.
Good chance ex some Pye -PMR kit. Why do I recall 10.695 MHz and thinking what a bodge.

10.240 MHz needed for the synthesiser ref but the 2nd IF conversion need 10.245MHz - so we just fudge it.
Bah ...only 23 - what do you expect?
Jon_G4MDC is offline   Reply With Quote
Old 11th Dec 2018, 11:12 pm   #59
G0HZU_JMR
Octode
 
Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 1,694
Default Re: 10M FM - any activity these days?

Yes, it's definitely worth changing the filtering in some of these radios, especially if the MC3357 FM chip is being used. The two options I had for 10FM when I was first licensed was a converted Cobra 148GTL-DX CB and a Trio TS430S HF radio. I bought the TS430S new and ordered the FM module for it. The performance of the FM module was quite poor so I ended up adding my own mixer to replace the one in the MC3357 chip and I also did something to improve the (all or nothing) s meter response. I also changed the 455kHz filter to one with a narrower bandwidth. I did this within about a week of buying the radio as it was no good as a serious FM radio without these changes.

Looking back in my logbook I can see I had a local contact on 10FM about 30 years ago and it was a UK special events station in Essex that was running on 10FM. i.e. they had a GB0 callsign. I can remember hearing repeaters on 10FM back then when conditions were good.

During Christmas and New Year there is often a brief bit of sporadic E activity so it is definitely worth having a listen on 10m SSB or FM now and again around the end of December.
__________________
Regards, Jeremy G0HZU
G0HZU_JMR is offline   Reply With Quote
Old 13th Dec 2018, 1:36 am   #60
sidspop
Triode
 
Join Date: Jun 2015
Location: West Bromwich, West Midlands, UK.
Posts: 31
Default Re: 10M FM - any activity these days?

What an interesting thread his has been.
In particular the 5 pages in Ham Radio magazine to tell people how to convert a Cobra, which could be done with half a dozen diodes.
We move on to SWM from yesteryear. Names such as Harvey Lexton, Brenda and Bernie, SMC, Lowes.......all gone.
I had a 1050 years ago, modded it with the links thing. Not bothered about repeater shift then. Funnily enough I picked one up in a deal a few weeks back, complete with Dymotape label on the front saying 10FM.
I also have an interesting Cobra 148, which I managed to get legalised in the CB amnesty, about 1984 ish?
It covers 26.000 to 30.000.
BCD thumbwheels, which then feed to 4 bit adders.
4 logic levels from bandswitch, adding 100 each time.
The outputs of both of these then feed to original 4 bit adders and then PLL.
I have been doing that radio for 30 years plus, and it has never had the covers on.
sidspop is offline   Reply With Quote
Reply

Thread Tools



All times are GMT +1. The time now is 5:36 pm.


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 - 2019, vBulletin Solutions, Inc.
Copyright ©2002 - 2019, Paul Stenning.