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Sunday, December 25, 2016

AWA BK 1929 QSO Party Recap

The AWA Bruce Kelly 1929 QSO Party wrapped up a week ago. Unfortunately I had a fairly small window of opportunity here for operating. I did make 5 contacts, though. All in Minnesota and Wisconsin.

Listening to my signal on my 75A4 I thought it sounded pretty good with just a hint of a musical tone due to antenna sway. Certainly it was up to 1929 standards but with enough personality to be recognized on today's ham bands.

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Now I'll start working on my station for the AWA Linc Cundall Memorial CW Contest. See http://www.antiquewireless.org/awa-linc-cundall-memorial-cw-contest.html

Thursday, December 15, 2016

AWA Bruce Kelly 1929 QSO Party

Last weekend and this coming weekend was the AWA Bruce Kelly 1929 QSO Party. For this event only transmitters of 1929 (or earlier) design/technology are allowed. I try to participate every year. See http://w0vlz.blogspot.com/search/label/AWA%201929%20CW%20Contest .

This year I again started out trying to get my Hull Hartley to sound reasonable on 80 and 40. See http://w0vlz.blogspot.com/2009/10/more-1928-hartley_21.html Somehow since 2009 something has changed giving my Hartley a raw AC buzz and some signal drift. Swapping out parts/tubes and cleaning all of the contacts did not help. As a final effort I moved the entire station away from the shack outside wall (nearest the antenna). It still drifted and had a  T7 to T8 tone...it went back on the shelf and down came my trusty TNT.

This coming weekend I plan to be on 80 with my  210 x 2 TNT running 10 watts in and about 3 watts out. The receiver will be my KX3 with PX3 panadapter. I've given up on using a vintage receiver for the BK. 80 meter noise is pretty loud here. I need all the help I can get to hear anyone. Visible in the photo besides my TNT transmitter and KX3 receiver with PX3 panadapter is the backside of my regulated HV power supply. The wood box visible in the near left encloses my 2.5/7.5 V filament supply. In the milk crate is a QRP watt meter and Triplet milliampere meter. Notice that I have a shaft extension on my TNT transmitter. This rig is sensitive to hand capacity. Moving my hand close to the normal tuning knob changes the transmitter frequency making it difficult to zero beat another station without this extension.

Friday, December 9, 2016

More on my 20 meter Endfed Zepp


I've always been a little worried about feed line loss in my portable antenna /  20 meter Endfed Zepp.

TV twin lead does have more loss then lots of other feed lines that may be used but it is light and we're talking about less than 15 feet of the stuff here. Estimates I've found on the web show .5 - 1 dB loss per 100' for dry, clean, matched TV twin lead. The loss for 15' then comes out around .1 dB. Since my intended use of this antenna is temporary QRP-in-th-Park sort of operating, keeping the twin lead clean and dry should not be a problem. If it's raining, I just QRT, packup and go home.

Loss due to mismatch at the antenna is the other issue. See K5DVW's Nov 2006 QST article posted at http://www.arrl.org/files/file/Technology/tis/info/pdf/q1106037.pdf Assuming that the EFHW wire presents a 3000 ohm load to the 300 ohm feedline then the SWR is about 10:1. Extrapolating off the left edge of K5DVW's figure 1 chart leads me to conclude that this 10:1 feedline mismatch adds another .5 dB loss for about.6 dB total. Feedline loss for 30' of RG-58 (about the most I'd want to carry any distance) feeding a matched dipole at 14MHz is .4-.5 dB.

It appears that the feedline loss difference between 15' of twin lead feeding an EFHW wire and 30' of coax feeding a dipole is negligible.

My classic 20 meter endfed zepp antenna with quarter wavelength feed does require a tuner. While in theory the feedline could be trimmed and stubbed to present a 50 ohm load to the transmitter (see http://www.mfjenterprises.com/antennatalk8.php ) it is sensitive to antenna configuration and adjacent objects. A tuner of some sort is required to take care of the variable mismatch, but, since it is close to 50 ohms, the tuner does not need to be "wide range".

So based on my observations for this antenna -
- Some sort of tuner is required (built into many QRP rigs these days)
- Feedline loss is essentially same as coax
- Allows flexible deployment (Vee, L, vertical, sloper)
- No ground (or radial or conterpoise) requirement
- Light weight
- Entire antenna system is off the ground
- Usually requires only one support
- Optimized for one band but usually can be tuned as a random length end wire for other bands