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d4d off frequency

ron mcmurray
 

my d4d is off frequency, low by 2khz . do i decrease or increase capitance. it's at 14.272.
thanks, ron
kc0tdj

Adam Rong
 

Ron,

If you measure by a frequency counter or other devices with a probe, the capacitance introduced by the probe will pull low the oscillator frequency, and 2kHz is a reasonable number.

You can receive the same station using D4D and a known calibrated commercial radio to know the difference.

Thanks,
Adam

在 2019年8月6日,上午7:44,ron mcmurray <hamshack@...> 写道:

my d4d is off frequency, low by 2khz . do i decrease or increase capitance. it's at 14.272.
thanks, ron
kc0tdj

ron mcmurray
 

i used my k2 to measure it.

Adam Rong
 

Ron,

Since the info is limited, I have to guess.

I suppose you have calibrated K2 frequency. Please confirm you did like one of these ways:
1. Use zero beat to test the carrier leakage from the D4D oscillator.
2. If you send 1500 Hz audio into D4D and triggered VOX, your K2 should zero beat two most strong frequencies at 14.0755 and 14.0725 MHz.
3. Send FT8 signal and receive in K2 and compare the audio frequency delta.

Thanks,
Adam


On Tuesday, August 6, 2019, ron mcmurray <hamshack@...> wrote:
i used my k2 to measure it.



--
Thanks,
Adam Rong

ron mcmurray
 

dont know what i did but its working on frequency now.
thanks for your help.
ron, kc0tdj

ron mcmurray
 

found the problem. power socket is off center in hole when in the case. grounding the collector of q4.  i put a nylon screw in to cure it. socket is flat on the board its built a little off i guess.
ron, kc0tdj

Adam Rong
 

Ron, I don’t understand the point. This is nothing to do with frequency accuracy. Also, nylon screw is not necessary if you follow my instructions to build.

Thanks,
Adam

在 2019年8月8日,上午4:56,ron mcmurray <hamshack@...> 写道:

found the problem. power socket is off center in hole when in the case. grounding the collector of q4.  i put a nylon screw in to cure it. socket is flat on the board its built a little off i guess.
ron, kc0tdj

ron mcmurray
 

the barrel or the power connector was touching the plated thru hole of the back plate.the screw in q4 grounds the collector to the back plate. it messed with the voltage,not sure if frequency was off or it just was not working right. easier to use nylon screw than try to make hole bigger
ron kc0tdj

Adam Rong
 

The barrel or the external ring of the power connector should be grounded so it is okay to touch the plated dc jack hole.

For TO-126 package transistors like Q4, the hole has insulation already so a metal screw and a thermal pad will do the work of insulation from the PCB panel.

Thanks,
Adam

在 2019年8月8日,下午10:17,ron mcmurray <hamshack@...> 写道:

the barrel or the power connector was touching the plated thru hole of the back plate.the screw in q4 grounds the collector to the back plate. it messed with the voltage,not sure if frequency was off or it just was not working right. easier to use nylon screw than try to make hole bigger
ron kc0tdj

ron mcmurray
 

the data sheet for the c1162 shows collector connected to the mounting hole, mine shows screw was shorting collector to ground.
ron, kc0tdj

Adam Rong
 

Ron,

It is correct that the C1162 collector connected to the back plate, but the back plate is insulated with the mounting hole because there is a layer of black insulator inside the hole, if you look closely.

Thanks,
Adam