Antenna Handbook 1937

Has anything changed in the maths since 1937?

Well perhaps the way we calculate and the calculators and computers we use to get the answer. Our test equipment and radio’s have also taken a great leap forward; I have smiths charts on my analyser these days where it used to be complicated and time consuming to get the resolution to complex number problems.

The link below takes you to Frank Jones antenna handbook

http://www.tubebooks.org/Books/Jonesant.pdf

Still valid today? – leave a reply 

I like to try some of the old designs and compare  the performance with some of the improved antenna designs we have today,( Roll on Field day 2021)  but mostly its the detail of the design description that leads to ideas for improvements. 

John (m0hfh)

Uk Antennas End fed half wave

Thinking about a suitable antenna for use with a kite i decided to purchase UK antennas multi band end fed.

end-fed-antenna-with-mounting-bracket-80-40-20-17-15-12-10m

It seemed sensible to test the antenna matching before attaching it to a kite however the half wave for 80m was too long to put up at my QTH so i swapped it out for a half wave on 40m and attached it to the matching unit; using a mini VNA and MFJ 259B  i set about matching the radiator. The starting point indicated resonance at 6.6mhz so trimming the length i slowly brought it to resonance at 7.04mhz with vswr of 1: 1.2. To achieve this i had to attach a counterpoise of 3m, my only criticism being there was no attachment point for a counterpoise.
The screen shot shows the WSPR test at 200mw from my QTH on the 09/08/2020.
A  CW QSO into Kazakhstan at 50 watts was also achieved, it seems to work well.

Conclusion
Great antenna IP65 rating with good mounting clamp setup will report back when i test the full 80m half wave antenna supplied with the unit at field day.

John m0hfh

2m Fox Hunt

The fox hunt on Wednesday evening turned into a damp affair and was attended by Mike g0jmd, Paul m0znb , Garry g7nvz and John m0hfh. Peter Barnes m0swn was the fox who had gone to ground in the Mundy Playing fields accompanied by Brittany M6LVB. First hound to see the fox was John m0hfh using body shielding and a hand held, second was Garry g7nvz and Paul m0znb bringing up the rear. We had a cream cup cakes as our prize and returned to rock street around 9.15, a fun evening.

End fed Resonant Half wave project

To help with construction a Photograph of the Primary and Secondary connection.

If you are using a single connection box keep the primary at one end and the capacitor used in the Tank circuit at the other.

Keep the connecting wires as symmetrical as possible

Boxes suitable for this project Screwfix.com  Part no. 33991 and 35121

80m ARDF testing Tonight

Weather is not great for this event however the Mundy playing fields has a car park. The 5 watt Transmitter will be operating from 19.00 hrs this evening, 3.568mhz CW and can be received in Alveston at 599 so try your receivers on the way over and report the distances. The second transmitter will be <1 watt @ 3.579.3 Mhz cw and will be at the Mundy playing fields in Thornbury;decode the Identifiers for both signals and report your findings via qrz or the website or to John m0hfh.

Both transmitters send the club callsign initially G4ABC , with a short message for just over a minute which is repeated at approximately 30 second intervals.

thanks

John

Chirp and Drift

The Fists CW club have some competitions (NOT CONTESTS)  organised for the bank holiday week and weekends 22nd to 27th of May.
www.https://fists.co.uk/activitiescalendar.html
If you have a vintage radio and would like to Chirp and Drift or warm it up for a few hours Rex and I will be around to help send or receive some slow morse.

How about some AM (amplitude Modulation) ! pre- arranged as its not a popular mode.
The 2m refresher looks interesting, 2 hours per day finishing at 9 pm, Rex and I will be operating from the ridge or Rex’s QTH with a beam for that event.

Let us know if you would like to join us for a cw qso 5 wpm or as slow as you can manage.

perhaps some practise at club on Wednesday.