[hpsdr] Hermes 144mhz

[Kjell Karlsen]

Hi Bent.

I am not sure if it is possible to just short the LP filter, it may be  
necessary to remove it. If just shorted, it will be in parallel to the  
signal and can attenuate the 144 MHz signal but I am not sure. The LP  
filter between U11 and U10 is is installed to reduce the aliasing noise  
 from U11 so if it is modified, the S/N on HF will be worse.

There will be a similar problem in the TX. If you just tap the signal  
between T1 and FL1, the filter will still be in circuit and may distort or  
attenuate the signal at 144 MHz. And the "long" coax to the external board  
will be in parallel to the signal when working on HF. It might be possible  
to switch in this tap by using a diode in series with the VHF signal and  
send a control voltage via the coax on 144 MHz.

I think you must also switch off the Vcc to the TX amplifier when  
transmitting on VHF.

It might work but has to be tested.

73, Kjell



På Thu, 11 Sep 2014 02:33:39 +0200, skrev Bent Andersen  
<eskolin at gmail.com>:

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