GEC Kenilworth transceiver - UK Vintage Radio Repair and Restoration Discussion Forum

unitelex · 26th Dec 2015, 4:07 pm

Seasonal greetings!

I have a GEC Kenilworth RC665.
It seems to be tuned for 160MHz PBR, at least on the transmit side.
It had a Selcall pcba which I removed.
I am considering converting it for the 2m band, adding a PLL synth.

Does anyone have the schematic? or any experience with this set or its conversion?

Thanks
Chris

G6Tanuki · 26th Dec 2015, 8:54 pm

If it's the same as the kit shown here:

http://www.qsl.net/gm8aob/pages_2/gec_kenilworth.htm

then be aware that it's AM and that since the 1970s that's been pretty much obsolete on 2M because everyone switched to FM for local/mobile/repeater operation.

Don't spend time/money on a conversion to then find there's nobody using AM!

unitelex · 26th Dec 2015, 8:59 pm

Hi, yes it is the one in your picture.
If I add a frequency synth, then conversion to FM on the TX should be easy enough, also for the RX conversion I can add a discriminator demodulator. I did that already on a good old PYE Cambridge

G6Tanuki · 26th Dec 2015, 9:16 pm

I admire your dedication !!

In times past when I was playing with converting Pye Vanguards/Cambridges/Westminsters to 2M/4M amateur operation if we came across an AM set we usually gutted it for spares because there were plenty of FM ones around which were easier to get going. If we wanted AM/FM we got ourselves a Pye Whitehall.

Same went for the Dymar "Lynx 2000" series of radios: the AM versions *could* be FMed if you were truly persistent but all the versions were dirt-cheap and it was easier to find a FM version than struggle with making an AM one work on FM [swapping the IF-filters to get the right bandwidth for the mode-in-use was a pain].

26th Dec 2015, 9:23 pm

I suppose you could use one of the very cheap 2m Chinese handhelds as a PLL modulator and RX. I got a dual band (2m 70cm) one for less than thirty quid, works well.

unitelex · 27th Dec 2015, 5:39 pm

Hmm... forgot about the IF filter bandwidth. The conversion did work on the AM10D Cambridge but I seem to remember the FM modulation was a little low, possibly due to the filter

G6Tanuki · 28th Dec 2015, 9:07 pm

IF issues were classically the big nuisance in PMR conversions: the early [up-to-mid-1960s] radios used 50KHz-wide receiver filters (because the transmitters were a bit drifty) - then they switched to 25KHz and subsequently to 12.5KHz.

If you were lucky and lived somewhere remote you could get away with wide filters - until someone local decided to hold a QSO on S21 when you were monitoring S20 and your squelch kept lifting on their occasional overmodulation.

AC/HL · 29th Dec 2015, 2:19 am

Kenilworth high band circuit.

unitelex · 31st Dec 2015, 2:55 pm

Hi G6Tanuki, Bill,
Thanks for your information and especially the schematic !

Following your good advice I have switched my attention to a Pye Westminster which I also have. It is 68-88MHz FM with 20 KHz filter. I have already re-tuned the RX input up to to 70.25MHz from 69.6MHz which of course was relatively easy. Now need to work on the TX which is currently tuned to 84.7MHz, and build or buy a pll frequency synth.
Is it better to have the synth VCO running at carrier frequency (tx) and carrier-10.7MHz for (rx) or can I use a lower frequency VCO and employ the xtal multipliers in the Westminster?

26th Dec 2015, 4:07 pm	#1
unitelex Hexode Join Date: May 2005 Location: Greater Manchester, UK. Posts: 498	GEC Kenilworth transceiver Seasonal greetings! I have a GEC Kenilworth RC665. It seems to be tuned for 160MHz PBR, at least on the transmit side. It had a Selcall pcba which I removed. I am considering converting it for the 2m band, adding a PLL synth. Does anyone have the schematic? or any experience with this set or its conversion? Thanks Chris

26th Dec 2015, 8:54 pm	#2
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,015	Re: GEC Kenilworth transceiver If it's the same as the kit shown here: http://www.qsl.net/gm8aob/pages_2/gec_kenilworth.htm then be aware that it's AM and that since the 1970s that's been pretty much obsolete on 2M because everyone switched to FM for local/mobile/repeater operation. Don't spend time/money on a conversion to then find there's nobody using AM!

26th Dec 2015, 8:59 pm	#3
unitelex Hexode Join Date: May 2005 Location: Greater Manchester, UK. Posts: 498	Re: GEC Kenilworth transceiver Hi, yes it is the one in your picture. If I add a frequency synth, then conversion to FM on the TX should be easy enough, also for the RX conversion I can add a discriminator demodulator. I did that already on a good old PYE Cambridge

26th Dec 2015, 9:16 pm	#4
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,015	Re: GEC Kenilworth transceiver I admire your dedication !! In times past when I was playing with converting Pye Vanguards/Cambridges/Westminsters to 2M/4M amateur operation if we came across an AM set we usually gutted it for spares because there were plenty of FM ones around which were easier to get going. If we wanted AM/FM we got ourselves a Pye Whitehall. Same went for the Dymar "Lynx 2000" series of radios: the AM versions could be FMed if you were truly persistent but all the versions were dirt-cheap and it was easier to find a FM version than struggle with making an AM one work on FM [swapping the IF-filters to get the right bandwidth for the mode-in-use was a pain].

26th Dec 2015, 9:23 pm	#5
Guest Guest Posts: n/a	Re: GEC Kenilworth transceiver I suppose you could use one of the very cheap 2m Chinese handhelds as a PLL modulator and RX. I got a dual band (2m 70cm) one for less than thirty quid, works well.

27th Dec 2015, 5:39 pm	#6
unitelex Hexode Join Date: May 2005 Location: Greater Manchester, UK. Posts: 498	Re: GEC Kenilworth transceiver Hmm... forgot about the IF filter bandwidth. The conversion did work on the AM10D Cambridge but I seem to remember the FM modulation was a little low, possibly due to the filter

28th Dec 2015, 9:07 pm	#7
G6Tanuki Dekatron Join Date: Apr 2012 Location: Wiltshire, UK. Posts: 14,015	Re: GEC Kenilworth transceiver IF issues were classically the big nuisance in PMR conversions: the early [up-to-mid-1960s] radios used 50KHz-wide receiver filters (because the transmitters were a bit drifty) - then they switched to 25KHz and subsequently to 12.5KHz. If you were lucky and lived somewhere remote you could get away with wide filters - until someone local decided to hold a QSO on S21 when you were monitoring S20 and your squelch kept lifting on their occasional overmodulation.

31st Dec 2015, 2:55 pm	#9
unitelex Hexode Join Date: May 2005 Location: Greater Manchester, UK. Posts: 498	Re: GEC Kenilworth transceiver Hi G6Tanuki, Bill, Thanks for your information and especially the schematic ! Following your good advice I have switched my attention to a Pye Westminster which I also have. It is 68-88MHz FM with 20 KHz filter. I have already re-tuned the RX input up to to 70.25MHz from 69.6MHz which of course was relatively easy. Now need to work on the TX which is currently tuned to 84.7MHz, and build or buy a pll frequency synth. Is it better to have the synth VCO running at carrier frequency (tx) and carrier-10.7MHz for (rx) or can I use a lower frequency VCO and employ the xtal multipliers in the Westminster?