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

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Old 22nd Nov 2017, 1:33 pm   #1
Argus25
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Default NZ made ZC1 MK2 Radio.

A while back I restored a ZC1 MK2.

I got it out again tonight. It has to be one of the best radios ever made. It TX/RX's 2-4 MHz and 4-8 MHz. Maybe this post will inspire others to fire up their vintage military radios.

I made some modifications to it (without drilling any holes). I noticed that the connector on the front panel, which was designed to feed a small lamp via a resistor, could be used to couple out a very tiny amount of the set's local oscillator or the TX oscillator signal. That way I could run my homebrew frequency counter (using TIL311 displays) which has an IF offset, to display the tuned (or transmitted frequency) the counter detects the level and switches out the IF frequency offset on transmit

Also I made a high impedance speaker to replace the headphones.

There are quite a few good stations still on shortwave in the 4 to 8 MHz zone. But I have a pantry transmitter with a variable RF output so I transmitted to the ZC1 at just under 2MHz tonight. The radio sounds great. I listened to a few song's such as Mr Hendrix's version of All Along the Watchtower.

I also managed to find a vintage pocket watch to fit in the watch carrier (photos attached)

This set is very reliable now, it runs a simple electronic plug in replacement for the original electromechanical split reed synchronous vibrator which I designed using germanium transistors and a coupling transformer which forces the main transformer into oscillation. I wrote an article on these power supplies and also how to get the most RF power out of a standard ZC1 on transmit into a 50R load and how to extract the L/O signal. etc.

I posted this article once before but it may be of use to others with the same or a similar radio:

http://worldphaco.com/uploads/ZC1_MK...R_SUPPLIES.pdf
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Old 23rd Nov 2017, 12:30 pm   #2
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Default Re: NZ made ZC1 MK2 Radio.

Hi Hugo,

Nice to see the picture of your ZC1 - it looks in excellent condition. A fellow VMARS member used to run his ZC1 on the regular 80m AM net on Saturday mornings. It always sounded very good and he often commented on the quality of the engineering.

Also, I must congratulate you on your superb article on the ZC1 modifications. I don't think I've ever seen a more professional looking piece of work. Thank you so much for posting the link.

I have recently refurbished a non-synchronous vibrator from a British R209 receiver and was astounded at the contamination by the rubber packaging compound.

Keith - G3XGW
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Old 24th Nov 2017, 11:15 am   #3
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Default Re: NZ made ZC1 MK2 Radio.

Quote:
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I have recently refurbished a non-synchronous vibrator from a British R209 receiver and was astounded at the contamination by the rubber packaging compound.
Keith - G3XGW
Keith, yes the rubber seems to degrade over time. I noticed that when it becomes liquid and tacky it deposits out on the contact surfaces. Then the contacts become insulated and stick together. When I restore these units I get rid of the original rubber. The melted rubber is also quite corrosive. Melted latex appears to attach aluminium in some cases too. The vibrators, when they are set up correctly with clean contacts do work well though. It always takes a scope to get the contacts perfectly adjusted.

I like your number 19 set !
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Old 24th Nov 2017, 12:07 pm   #4
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Default Re: NZ made ZC1 MK2 Radio.

I have a couple of examples of the early ZC1 fitted with two meters. Both are in totally derelict condition with lots of missing parts, but I did an initial assessment a few years ago and concluded that it might be possible to reconstruct one good one out of the two. Normally the law of Sod dictates that two hacked-about examples will be missing the same parts, but unusually not so in this case.

Whether I will ever find time to do anything with them is another matter entirely.......

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Old 24th Nov 2017, 12:56 pm   #5
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Default Re: NZ made ZC1 MK2 Radio.

Andy,

That is probably the ZC1 MK1, some appeared to have a meter and a watch holder and others two meters. I think those ones use a non synchronous vibrator and a valve rectifier combination in the power supply.
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Old 25th Nov 2017, 10:54 am   #6
Peter.G0DRT
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Default Re: NZ made ZC1 MK2 Radio.

I have the Mk2 version.It was fitted with a mains p.s.u.which was a real bodge job.I managed to acquire an original 12volt unit for which I built an electronic vibrator.
There were other issues which were finally resolved and the set is working fine.I use it on both 160 and 80 mtrs a.m.and c.w.It is a very nice set to use.
There is a lot of info on the ZC1 Radio Club Site which includes mods.
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Old 25th Nov 2017, 11:35 am   #7
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Default Re: NZ made ZC1 MK2 Radio.

Quote:
I have the Mk2 version.It was fitted with a mains p.s.u.which was a real bodge job.
Peter,

Yes as I mentioned in the article on mine that I posted the link to, many ZC1's were subjected to fairly extreme modifications. At the time though I don't think the folks doing this saw the ZC1 in the same sort of historically significant way we do today. So they were not shy to drill holes and radically change the circuits.

One ZC1 MK2 I have was radically modified, it was made into a "Marine Transceiver". They modified the oscillators to be crystal oscillators, a Pierce circuit (actually pretty clever). It took me a while to undo all the mods and convert the set to original.

The quality build of the ZC1 is one of its most awe inspiring features. I'm a pretty tough judge of the builds of many radios and it takes a lot to get me excited about a design, but the ZC1 sure does it for me.

Hugo.
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Old 25th Nov 2017, 11:48 pm   #8
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Default Re: NZ made ZC1 MK2 Radio.

Looks like the ultimate 19 set.

Any internal pics after all that build up about build quality?
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Old 26th Nov 2017, 10:26 am   #9
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Default Re: NZ made ZC1 MK2 Radio.

Quote:
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Looks like the ultimate 19 set.
The difference is that the ZC1 followed the traditional arrangement of separate transmitter and receiver. The 19 set, as far as I'm aware, was the first true transceiver .
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Old 26th Nov 2017, 2:39 pm   #10
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Default Re: NZ made ZC1 MK2 Radio.

Quote:
Originally Posted by Herald1360 View Post
Any internal pics after all that build up about build quality?
I'll look around and see if I have any internal photos.

Here are some internal views on an NZ website:

http://www.zc1-radioclub.org.nz/zc1_...al%20views.htm
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Old 26th Nov 2017, 3:01 pm   #11
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Default Re: NZ made ZC1 MK2 Radio.

Lots of room under the chassis compared with the 19 set - a dream to work on!
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Old 27th Nov 2017, 4:31 am   #12
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Default Re: NZ made ZC1 MK2 Radio.

Quote:
Originally Posted by Keith View Post
Lots of room under the chassis compared with the 19 set - a dream to work on!
One of the lovely parts about it was the TX antenna loading coil and switches. In fact the design of that, modified to a little lower frequency, would make a great loading coil design for a wire antenna for a pantry transmitter.
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Old 29th Nov 2017, 9:52 am   #13
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Default Re: NZ made ZC1 MK2 Radio.

I found a couple of photos, one showing some of the inside of my ZC1, and another of the germanium transistor vibrator replacements I made. The plan was to make an electronic vibrator replacement that matched the quality of the ZC1 (not an easy task) and looked at home inside the unit.
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