[Elecraft] K3 with 2m tvtr - power control feature request

[Harald Fritzsche]

Hello All,

unless otherwise expected, there is no AGC in the signal path of K144VX.
Therefore the dbm setting is not so accurate on output power as expected.
Furthermore, since there are 2 bandpasses in sequence (28MHz and 144MHz) the ripple of those bandpasses creates frequency dependend output power.

My solution for the Kuhne-Microwave transverters is:
1. setting Outputpower on 144.100 MHz to 2,5W, with maximum dBm setting with this R87 TX GAIN potentiometer
2. set the TX GAIN in the Microwave transverter to a value that allows maximum microwave output at 0dBm setting. (measurement)
3. checking frequency dependency and dBm setting dependency of the microwave output and create a graph or table for proper settings (for me during contest)
 
Yes -10dBm setting will not lead to a 10dB reduction on micowave power side, i measured this only for 13cm, it drops from approx 15W at max down to 6 at min.

This allows me to stay in a safe area, which is fully sufficient for me.

Hope i made it understandable.

Good Luck and many DX with Microwaves.

BTW: a feature missing on K3 is to program frequencies above 25GHz :-(

vy73
Harald
DD0VS
 
 

Gesendet: Donnerstag, 06. Juli 2017 um 21:06 Uhr
Von: "Gary Hembree" <n7ir at cox.net>
An: elecraft at mailman.qth.net
Betreff: Re: [Elecraft] K3 with 2m tvtr - power control feature request
I have made the same observations with my K3/K144XV, vintage 2010: 8 Watts out at 0dBm in and 4 Watts out at –10dBm in, all power measurements done on calibrated Bird and Boonton meters. The transverter performs very well and gets clean signal reports, so it is not excessively non-linear. The measured spectrum, to more than 1 GHz, is clean with no sign of oscillations.

This behavior must be the result of a transmit AGC circuit in the K144XV. Harald has apparently found its upper limit adjustment potentiometer.

73
Gary, N7IR
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