Re: 9 MHz Crystal in a TR-4
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These are quite inexpensive:
I presume the non-series type are what I would need?
Thanks, Barry - N4BUQ
From: "Steve Wedge, W1ES/4 via groups.io" <w1es@...>
To: "DRAKE-RADIO" <[email protected]>
Sent: Wednesday, April 23, 2025 11:26:57 AM
Subject: Re: [DRAKE-RADIO] 9 MHz Crystal in a TR-4
From what I have seen, Drake used the same basic circuit for their CO in both the TR-3/4 and the T-4(any), aside from the crystal. I have seen the smaller crystals used by Drake in their TR-4¡¯s. AF4K uses the same width but it¡¯s a very short height. ?I¡¯ve used these crystals in a couple of Twins (5645) and they¡¯ve worked fine.
New ones aren¡¯t cheap anymore (around $24, IIRC) but work fine.
If the lowest frequency you can adjust is almost 300 Hz too high, then you will likely have trouble getting on-centre.,
The best you¡¯ll probably hear with a receiver will be a very fast warble. ?The transmitter and receiver can only ¡°rubber¡± their crystals by about 400 Hz or a tad more.
73,
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Wed, Apr 23, 2025 at 11:12 AM, n4buq <n4buq@...> wrote: I'm still looking into my TR-4's 9 MHz oscillator. Earlier, I said I could wrap a coil of wire around the oscillator tube (V16) and measure the frequency but apparently I was misremembering something because I tried that last night and I could not get the counter to trigger on anything close to 9 MHz so I just used a 10:1 oscilloscope probe which worked fine.
Unfortunately, I am not able to get the oscillator exactly on 9 MHz. C130 will adjust it down to about 9.000280 MHz but I presume I should be able to swing the oscillator very slightly above and below 9 MHz leading me to believe the crystal has "drifted" upwards just a bit and because of this, I'm not quite able to get one of the filters to respond correctly. IIRC, the LSB filter will respond down to inaudible as I approach zero-beat with the calibrator; however, USB fades out long before zero-beat and I think that's due to the CO being too high.
Any suggestions on a fix? I presume baking it might bring it back down but if that doesn't work, then I'd like to replace it. They're available new in that form factor (HC-49) but I'm not sure about what other characteristics I'd need to consider. I presume this isn't a series crystal and should have an appropriate load capacitance but perhaps other factors may need to be considered.
Anyone know the specs for that crystal?
Thanks,
Barry - N4BUQ
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