[DSP-10] DSP-10 troubleshooting - false alarm

[Don AE5K]

On 04/12/2013 03:54 PM, Don AE5K wrote:
> On 04/12/2013 03:45 PM, Joe wrote:
>> Don,
>>
>> I think that the jumper between the two RCA connectors is the 
>> transmit RF before the PIN diodes.  This is where I place an 
>> attenuator when I need only a Milli-watt of excitation.  Maybe you 
>> could measure the power there.  Or is the jumper missing?
>>
>> Joe WB8DNO
> Hi Joe, and thanks for the message.  I think you mean the r.f. tx 
> output/input connectors on the enclosure.  I use BNCs here instead of 
> RCA.  I do have the jumper in at this point, but I will take it out 
> and connect the power meter directly to the P3 power out from the 
> 2N5109 final amp to eliminate the possibility of those PIN diodes not 
> working right.  In previous messages, the PIN diode that I was 
> referring to was at the input to the tx amplifier chain consisting of 
> U4 U5 and Q2.

It was a good idea to try, but that is not the problem.

BTW, power is back up to +3.6 dBm now, was -0.6 dBm.  This is measured 
with the BNC jumper in place, i.e. PIN diode D2 is in the circuit.  
Measuring power directly at the BNC jack named TX OUT (connected to P3), 
I get +4.3 dBm, so it appears there is a loss of about 0.6 dB involved 
with the PIN switch.  Sound reasonable?

Don AE5K