[Elecraft] [K2] No Transmit Power

[Brian Denley]

Don:
I brought home a high end 500 MHz Agilent scope from work along with it's 
10X probe.  It also has a 20 mV per division small signal capability.  This 
should at least allow me to take more accurate measurements (peak to peak) 
of the transmitter section.  More later.  thanks again for the help,.
Brian
Brian Denley
http://home.comcast.net/~b.denley/index.html
----- Original Message ----- 
From: "Don Wilhelm" <w3fpr at embarqmail.com>
To: "Brian Denley" <b.denley at comcast.net>
Cc: "Elecraft Reflector" <elecraft at mailman.qth.net>
Sent: Tuesday, September 07, 2010 12:59 AM
Subject: Re: [Elecraft] [K2] No Transmit Power


>  Brian,
>
> Since you are unable to measure any RF voltage, I am going to start at the 
> beginning - proper assembly of the RF Probe.
>
> The RF probe voltage is not read "across" the 4.7 meg resistor, it is read 
> between the end of the 4.7 meg resistor and ground.  That is an important 
> difference.  In other words, the 4.7 megohm resistor is in series with the 
> detector.  Since the nominal input resistance of a DMM is 11 megohms 
> (established in the "old days" of VTVMs), that resistance in series with 
> the 11 megohms will cause the DMM to indicate the RMS value of the RF 
> voltage being measured.  There are other techniques that will provide DMM 
> readings that indicate the zero to peak RF voltage, but the RF probe parts 
> provided with the K2 will indicate the RMS voltage values when used with 
> most DMMs.
the steps listed in Appendix E of the manual under Transmit
>>> Signal Tracing.
>>> When you get to the points to measure on page 14 (assuming you do not
>>> find a problem with the VFO or BFO), the RF voltages will be HIGHER than
>>> the expected value because you do not have enough transmit output.  What
>>> you are looking for is the first point where the RF voltage is LOWER
>>> than the expected value.  That point is just beyond the failing stage,
>>> and you will know which stage to examine in detail.
>>> Only after your K2 is operating properly for RF output will you see the
>>> expected values - go with the higher or lower criteria.
>>> Don
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Elecraft at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>