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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 18th Jan 2021, 10:55 pm   #1
Triple M
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Location: Uffculme, Devon, UK.
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Default 70mhz/4M transverter or TXR wanted.

Have decided that I need to experience 70mhz so looking for a suitable transverter, or if the price is right a dedicated transceiver (FM is ok for the moment)
Microwave Modules, SEM, RN Electronics plus other 1970/80's transverters, solid state or valve would be of interest, or other makes (home brew?) that will run on a 28mhz IF

Let me know what you have?

Thanks and 73 de G0HPS
Glenn
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Old 19th Jan 2021, 8:14 am   #2
M0AFJ, Tim
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Default Re: 70mhz/4M transverter or TXR wanted.

Hi Glenn, probably cheaper to buy a new one from the Transverter Store. They have a new range out with a better mixer and high stability oscillator.
Don’t worry about buying from the Ukraine, the company are very responsive.

https://transverters-store.com/4m.htm

73, Tim M0AFJ
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Old 19th Jan 2021, 8:53 am   #3
Jon_G4MDC
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Default Re: 70mhz/4M transverter or TXR wanted.

28MHz is a common IF for 4m but actually it's a poor choice.
Wanted is 28+42=70 but 42x3 - 28x2 =70 happens as well. It's an in band spur so it can't be filtered. As you transmit further up the band the spur moves down out of band to QRM adjacent services.

29MHz is better since the spur is by now at 65MHz and somewhat filterable.

21MHz is better still since all the spurs are miles away.

Various designs try to bury the spur by using very low mixer levels and lots of post mixing gain (noisy output results) or they tune the spot where the spur is right under the carrier and take their plots there.

Much better to use 21 and 49MHz when full advantage can be taken of the drive level of the parts.

Last edited by Jon_G4MDC; 19th Jan 2021 at 8:59 am.
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Old 20th Jan 2021, 12:41 am   #4
Triple M
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Default Re: 70mhz/4M transverter or TXR wanted.

Thanks both and noted on the Transverter store!

Cheers
Glenn
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Old 20th Jan 2021, 11:00 am   #5
GMB
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Default Re: 70mhz/4M transverter or TXR wanted.

For FM the Clansman RT351 military sets are pretty cheap and cover 6m and 4m.
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