I have now completed the build of my Miss Mosquita 3 a 40m CW transceiver.
I decided to mount all controls and connectors on the front as I feel this is a better configuration for a portable rig. The antenna connector was swapped to the RCA to save some internal space, and is reasonably common amongst qrp gear, so not too out of place.
The push button ‘f’ is for the freq-mite which announces the operating frequincy in morse code
Upper left is the Freq-Mite pcb, just below it is the Simple Keyer from QRP Kits with its Peizo mounted on the perf-board.
TX power, at 10.0v- 2.4W, 12.0v- 3.4W and 13.8v- 4.4W
Drift is around 180Hz in the first minute and a further 300 Hz by the 5min mark, it then settles down and is not noticable on all but the longer qso’s.
Tuning range, 6997 to 7046 KHz (49KHz) and quite linear over the full range.
With the current bad conditions the need to run 80m during the day for SOTA activations has caused me to visit antenna options that would allow me to run 80 with a “minimum” amount of wire.
My normal SOTA / WWFF antenna is an end fed of around 25m with a 6m counterpoise, this is then matched to 50 ohm using an external L Match. This configuration is fine on 40m and up, but is too close to a quarter wave length on 80m to match well. Continue reading →
The vertical has had a number of runs since the first post.
I have not actively compared its performance to my end fed antenna. But it seems to be no less efficient as I have worked a few JA station on 18MHz when using it.
The design remains similar with the exception of adding a 1:1 current balun. This was introduced to isolate the coax from the antenna system, as I noted some variation in VSWR as the coax was moved. This was discussed here on the SOTA reflector (look for post #7)
I have remained with the3.7m radials but I have increased the number to 8 (yet to be tested).
After reading An experimental look at ground systems for HF verticals (second link below) I may increase that number to 16.
Naturally the internet is most people go to when it comes to research, to date I have turned up three items of interest
I have also found some interesting reading by Rudy N6LF, Rudy has done a huge amount of work with antennas. two articles caught my with regard to radials for vertical antennas;
First one, on this page look for Series of QEX articles on ground system experiments
The summary of these articles are covered in this document Download QST March 2010 Ground Systems
The second one looks at radial length for shorter verticals, one this page look for Are the lengths of radials related to the height of a vertical? to find the article Vertical height versus radial system