Mark,

You could try to find an original antenna for the TRC-7 and connect it to the handheld radio. The antenna would be period correct. One could also copy/build the antenna and paint it green. The antenna should be set up in the clear, above the test for best coverage. This would work far better than a rubber ducky antenna.

Ed, KI6R

---------- Forwarded message ---------
From: MARK DORNEY <mkdorney@aol.com>
Date: Sat, Oct 4, 2025 at 5:59 AM
Subject: Re: [MRCA] CR-1 crystals for an RT53B/TRC-7 RT
To: Edward Larsen <ki6rcm98@gmail.com>

Hello Everybody,

Thank you for all the very helpful information. Here’s the backstory.

At a recent commemoration ceremony, we had a flyover by a WW2 warbird. The warbird was supposed to be coordinated to fly over at a specific time during the ceremony. Coordinators had a modern handheld radio with a “rubber Duck” antenna for use at the ceremony site to be used to communicate with the aircraft to help insure that coordination. The frequency they use for admin stuff when working the aircraft is 130.30 MHz. My WC-52 was at the site, in town, with a red panel marker draped on the roof in the hope that it would aid the crew of the aircraft in spotting us on the ground. The aircraft had GPS navigation onboard, which did enable it to fly directly over the site of the ceremony. The timing, however, was a bit off. Comms using the handheld were sketchy at best - basically, we could not communicate with the aircraft. Short range radio with a rubber duck antenna ( great for close in stuff, not so good for comms with an aircraft in the air, since the aircraft would only be in range for a minute or two). The crew were also not able to pick out the bright red panel marker we had on the ground, since the ceremony site was in town, and the crew were not able to pick it out of all the ground clutter. The HF set I have in the WC ( BC-654-A ) was useless for this operation, since the aircraft was not equipped with HF radios.

So how to fix this? We either come up with an HF set for the aircraft ( not happening) or we come up with a VHF set on the ground, set to an admin frequency ( there was no need for us to talk to a control tower or chit-chat a lot with a bunch of other folks in the air). So we started exploring options for a ground radio better than a handheld with a rubber duck. Well, anything that gets installed in the WC has to be WW2 vintage, and has to work. Power supply is 12 volt DC, supplied by the vehicle ( typical for WW2 vehicles modified for use as radio vehicles ). The TRC-7 uses the same battery as the SCR-300/BC-1000 radio ( BA-30) . I have two power supplies for the BC-1000: one is an older civilian vibrator power supply designed to use a 6 volt battery - make a holder for the 6 volt battery, and the vibrator power supply and configuration is basically the same as the original design ( manpack portable). I also have a WW2 issue PP-114, which is the vehicle mounted power supply for the SCR-300/BC-1000 that is used when that radio is mounted on a vehicle ( one use was a US Locust tank - replaces the BA-30 battery). No modification to the radio is needed to use either one of the power supplies. While a WW2 era radio not the best option for this job, the TRC-7 in the WC really is the only option for a working WW2 ground forces VHF set in the WC. I’m not too enthusiastic about putting a VHF set in the WC, but it is what it is.

The third (best) option is for the group doing these ceremonies to set up a better modern air frequency radio that uses something better than a rubber duck antenna, and if they had to, set it up on the a spot at the ceremony site not accessible or really seen ( like in a tent) by the general public if they want the best chance to actually talk with an aircrew in the air. Either build a better antenna that can be used with the handheld to replace the rubber duck, or buy a better radio with a better antenna. An antenna is an antenna to the general public- to most just about any antenna wouldn’t be seen as being out of place. So far, these two options have not been met with a lot of enthusiasm.

Mark D.

WW2RDO

“In matters of style, float with the current. In matters of Principle, stand like a rock. “. - Thomas Jefferson

Sent from my iPhone

On Oct 3, 2025, at 10:23 PM, Edward Larsen <ki6rcm98@gmail.com> wrote:

Mark,

You have a worthy project. Some of the old WW2 era equipment is fascinating in both design and function.

I looked through my junk box. I have the transmit crystal in an FT-243 package. It tests at 7238.709 kHz in my crystal tester. It would likely adjust to the needed 7238.888. You would need to attach it to CR-1A case pins, which are larger.

I don't have a receive crystal, but there may be options. The receive crystal oscillator uses a dual triode tube, with one triode as a fundamental oscillator, and the second triode as a multiplier. This means you may be able to use a crystal frequency at a non-recommended harmonic ratio in the 11x to 17x range and still get the harmonic generator to tune-up. The oscillator circuit may need some slight modification if either the fundamental or harmonic tune-up doesn't work correctly.

Other possible receive crystal frequencies

Harmonic - Frequency

17 - 6976.470 kHz

16 - 7412.500

15 - 7906.667

14 - 8471.428 (desired multiple)

13 - 9123.077

I have a 6961.025 kHz in a CR-1B case. I doubt the oscillator circuit could be tuned to 6976.470. One could try to disassemble the crystal and carefully polish the quartz wafer to raise frequency about 15.4 kHz. In the old days hams often did this.

I have I have 7407.671 kHz in FT-243 case. This would need to be raised about 4.8 kHz. There is some chance the oscillator circuit could be tuned or modified to move the crystal this far without a quartz wafer polish.

Lastly, I have 8450.121 kHz in FT-243 case. It would need to be lowered about 21.3 kHz by oscillator circuit adjustment. I doubt the crystal could be pulled this far.

I would be very careful putting that old transmitter on-the-air. It won't meet FCC specs for spectral purity, harmonics or other spurious radiation. It may interfere with others in the VHF/UHF bands.

Let me know if you need any of these crystals. You can have them for shipping/packaging cost, or simply send me a shipping envelope and I'll send them to you. Let me know what you want to do.

Ed, KI6R

SaddleBrooke, Az 85739

---------- Forwarded message ---------
From: Edward Larsen <ki6rcm98@gmail.com>
Date: Fri, Oct 3, 2025 at 4:27 PM
Subject: Re: [MRCA] CR-1 crystals for an RT53B/TRC-7 RT
To: MARK DORNEY <mkdorney@aol.com>

Hello Mark,

I found the manual at archive.org. It looks like the transmit LO multiplies by 18, thus the transmit crystal for 130.3 MHz would be 7.2388888 MHz.

The receive IF is 12 MHz and it uses low side LO, thus the receive LO frequency for 130.3 MHz is 118.3 MHz.

The receive LO is an odd arrangement of a harmonic generator followed by an amplifier that is tuned to multiply from 11 to 17 times. The receive crystal must be in the 8.00 to 8.47 MHz range. The needed harmonic in the range of 11x to 17x is calculated. I calculate 8.4714285 MHz for the receive crystal using the 14th harmonic.

I'll check my crystals to see if I have any of these. I will be surprised if I do. I'll let you know.

Tuning the unit will be a little tricky. One will need to know how to tune the harmonic generator in the receive LO, to the correct (14th) harmonic. The electronics technicians back in the 40s knew their stuff. They likely used wave-meters or grid-dip meters to verify the correct harmonic.

For 130.3 MHz TX/RX:

TX crystal: 7.2388888 MHz

RX crystal: 8.4714285 MHz

On Fri, Oct 3, 2025 at 2:47 PM MARK DORNEY <mkdorney@aol.com> wrote:

Hello Ed.
Looking to set up 130.30 MHz. Thanks.

73

Mark D.
WW2RDO

“In matters of style, float with the current. In matters of Principle, stand like a rock. “. - Thomas Jefferson

Sent from my iPhone

On Oct 3, 2025, at 11:14 AM, Edward Larsen <ki6rcm98@gmail.com> wrote:

Mark,
I have some CR-1A crystals. What fundamental frequency do you need?
Ed
KI6R, Az

On Thu, Oct 2, 2025 at 7:32 PM Jason WA6BBQ <w6iee.73@gmail.com> wrote:
Look into qrp-labs.com ProgRock2. It’s actually a synthesizer that runs off of 5 volts.

I modified a TRC-77 with two of them, and it works super, easily gives me 6 transmit and 6 receive frequencies , and I can change the T/R frequencies at will.

It will take a little work to adapt to your application, but still easier and vastly cheaper than unobtainium xtals.

Unfortunately, it’s a British company that ships from somewhere in Turkey, so you will be paying some tariffs and related fees.

Jason WA6BBQ

On Thu, Oct 2, 2025 at 16:50 MARK DORNEY via MRCA <mrca@mailman.qth.net> wrote:
From: MARK DORNEY <mkdorney@aol.com>
Date: October 2, 2025 at 5:42:03 PM EDT
To: mailman@mrca.qth.net
Subject: CR-1 crystals for an RT53B/TRC-7 RT

Hello Everybody,
I’m putting together an RT53B/TRC-7 VHF RT. The one frequency of real interest is 130.30 MHz ( the set is to be used when a real WW2 C-47 is dropping supplies/paratroops at events). There hasn’t been a decision on what second frequency is to be installed. The Crystal holders are the CR-1. Looking for the crystal holders and a somebody that cuts custom crystals? Any help is appreciated

Mark D.
WW2RDO

“In matters of style, float with the current. In matters of Principle, stand like a rock. “. - Thomas Jefferson

Sent from my iPhone
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