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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
|
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
|
I'd try just adding a small cap across the xtal or from xtal to ground, or across the trimmer.
280Hz isn't far, I'd try 5-10pf maybe.
?
73,
Gary
WB6OGD
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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
|
I'll give that a try.
Thanks, Barry - N4BUQ
I'd try just adding a small cap across the xtal or from xtal to ground, or across the trimmer.
280Hz isn't far, I'd try 5-10pf maybe.
?
73,
Gary
WB6OGD
|
Hi Barry,
Since the oscillator is working and sounds like it is stable, the possibility is that a capacitor in the area has dropped in value a bit, or it may just be aging of the crystal. Try putting a 5pF capacitor across the crystal and see where it goes. This will likely solve your problem.
Regards,
Clint, VE3CMQ
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-----Original Message----- From: [email protected] < [email protected]> On Behalf Of n4buq via groups.io Sent: Wednesday, 23 April 2025 10:12 To: DRAKE-RADIO < [email protected]> Subject: [DRAKE-RADIO] 9 MHz Crystal in a TR-4 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
|
Gary, Clint,
Great call!? I happened to have a 2pF SM and I placed it across the existing variable cap.? I now can get 9.000000 MHz with about 1kHz swing on either side.? The two sidebands now sound just like they should.? I can get a zero-beat on both sides with almost exactly the same frequency response as I tune through the calibrator signal and switch sidebands.? Very nice to have this working!
Thanks again, Barry - N4BUQ
I'll give that a try. Thanks, Barry - N4BUQ I'd try just adding a small cap across the xtal or from xtal to ground, or across the trimmer.
280Hz isn't far, I'd try 5-10pf maybe.
?
73,
Gary
WB6OGD
|
Steve,
While I now have the oscillator on frequency with an additional 2pF cap across the trimmer, I may still try a newer crystal.? I checked and AF4K doesn't stock 9 MHz in any of the forms they sell.? I may just try one of Mouser's crystals.? They're certainly inexpensive enough.
Thanks again, Barry - N4BUQ
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
|
I¡¯m surprised they don¡¯t have 9 MHz.?
Steve Wedge, W1ES
Time flies like an arrow. Fruit flies like a banana.
On Wed, Apr 23, 2025 at 20:09, n4buq < n4buq@...> wrote:
Steve,
While I now have the oscillator on frequency with an additional 2pF cap across the trimmer, I may still try a newer crystal.? I checked and AF4K doesn't stock 9 MHz in any of the forms they sell.? I may just try one of Mouser's crystals.? They're certainly inexpensive enough.
Thanks again,
Barry - N4BUQ
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
|
Glad it worked for you Barry!? It¡¯s an old trick and a lot less expensive than a new crystal!
?
73, Clint, VE3CMQ
?
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From: [email protected] <[email protected]>
On Behalf Of n4buq via groups.io
Sent: Wednesday, 23 April 2025 18:13
To: DRAKE-RADIO <[email protected]>
Subject: Re: [DRAKE-RADIO] 9 MHz Crystal in a TR-4
?
Great call!? I happened to have a 2pF SM and I placed it across the existing variable cap.? I now can get 9.000000 MHz with about 1kHz swing on either side.? The two sidebands now
sound just like they should.? I can get a zero-beat on both sides with almost exactly the same frequency response as I tune through the calibrator signal and switch sidebands.? Very nice to have this working!
?
?
I'd try just adding a small cap across the xtal or from xtal to ground, or across the trimmer.
280Hz isn't far, I'd try 5-10pf maybe.
?
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?
Barry wrote:
?
The Mouser crystal may work fine, but I am compelled to point out that AF4K Crystals does stock 9.0 MHz crystals.?
?
You can find 9.0 MHz in both HC-6 and HC-49 holders here:
?
?
They are found in the IF/SSB/BFO/Filter crystal section:
?
?
Good luck with your project.
?
?
73?? Steve? WD8DAS??
/??
--------------------------------------------------------------------??
Radio is your best entertainment value.??
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?
?
?
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Well, that's embarrassing.? I thought I had looked in that very category but apparently not or else, I missed it in plain sight!.? I did think it was odd they they wouldn't have it.
Thanks, Steve, for pointing that out.
Barry - N4BUQ
?
Barry wrote:
?
The Mouser crystal may work fine, but I am compelled to point out that AF4K Crystals does stock 9.0 MHz crystals.?
?
You can find 9.0 MHz in both HC-6 and HC-49 holders here:
?
?
They are found in the IF/SSB/BFO/Filter crystal section:
?
?
Good luck with your project.
?
?
73?? Steve? WD8DAS??
/??
--------------------------------------------------------------------??
Radio is your best entertainment value.??
--------------------------------------------------------------------??
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?
?
?
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Gary WB6OGD