[VHFcontesting] Total newbie questions about 2m and 70cm antennas and receive filters

Steve Kavanagh sjkavanagh1 at yahoo.ca
Tue May 21 08:08:27 EDT 2013


John:

Here's a start on some of your questions.....I too started out as an HF contester but have been spending more time on VHF than HF for many years.

(1) A dipole on 6m will get you some QSOs.  It's what I use in my Rover setup.  But as you can imagine, a beam is better !

(2) There is an explanation of antenna spacing on the Directive Systems website:

http://www.directivesystems.com/

Look in the "APP notes" section.  Generally speaking, smaller spacings often work, but you can be confident with the rules provided in that app note.

(3) An omnidirectional antenna will probably only be of help if it has significant gain (i.e. several stacked halos).  A Yagi usually has gain in the sidelobes about equal to a single halo.  The InnovAntennas beam might be different - they go to a lot of effort to keep the sidelobes down.

(4) One factor reducing your rotor spinning will be that most of your 70 cm QSOs will probably be done by moving people from 2m, so at least you won't need to turn the rotor between those QSOs.

(5) There's some very basic pointers (from an Ontario perspective) on the Contest Club Ontario website at

http://www.va3cco.com/VHFContestPrimer.pdf

And more on KC9BQA'a blog at

http://kc9bqa.com/?p=5931

(6) Most likely you won't really need the Inrad filters unless you have some very loud locals who like CW.  If they are on SSB you will probably have more problems with their splatter which can not be fixed by IF filtering.  The number of signals you hear at one time is normally much less than on HF and they are spread out more, with the possible exception of a good Sporadic E opening on 6m.  The stock DSP CW filtering will likely work well enough, at least to start with.

(7) Regarding the "is this enough power to have fun" question....it really depends on you.  The QSO rate will certainly be much less than Sweepstakes or CQWW (and would be even if you had a kW, most of the time !) so if rate is your main turn-on it may not be very much fun.  But to me, each QSO with a distant station on bands which most hams think are only good for local ragchews provides a bit of challenge which keeps me in the chair.

73,
Steve VE3SMA




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