[Elecraft] OT: Antenna ideas for a cheap ham

[Walter Underwood]

Right. That makes sense.

Though the worst case would be a 2:1 SWR if both are resonant, because the feed point impedance would be 1/2 what is expected. Not the end of the world.

A 40m dipole isn’t quite resonant on 15m anyway, so having both might make for more broadband 15m behavior with fewer broadside nulls. The ARRL Handbook includes a design with capacitance stubs to fix the resonance on 15m.

My setup is an 80/40/20 fan dipole with a neat trick. The 80m dipole is center loaded, and the center section is cut to resonate on 20m. In parallel with that is a full-sized 40m dipole. The loaded 80m element is just a few feet longer than the 40m element. 

That is the 3B2080LFAN from Hy Power Antennas. Good construction at a good price and a clever idea.

http://www.hypowerantenna.com/products/fan-dipole

Walter Underwood
wunder at wunderwood.org
http://observer.wunderwood.org/


On Sep 14, 2014, at 12:16 AM, Bill Frantz <frantz at pwpconsult.com> wrote:

> Fan dipoles depend on the relatively high impedance on the fan pieces that are for other bands to send most of the energy into the tuned fan. If you are using fans for 40 and 15, the energy will be split between them on 15M which isn't what you want.
> 
> BTW - My combination of a 160M dipole commonly fed with an 80M inverted V at 90 degrees to the 160M dipole works quite well on 15 meters. The cocoaNEC model shows good performance with 4 major lobes arranged more or less in the direction of the 160M wire.
> 
> 73 Bill AE6JV
> 
> On 9/13/14 at 11:14 PM, wunder at wunderwood.org (Walter Underwood) wrote:
> 
>> Eh? A 40m dipole is pretty close to resonance on 15m already, so how can you avoid that. In fact, all dipoles are resonant at odd multiples of half waves, so this is impossible to avoid.
>> 
>> Could you clarify the issue here?
>> 
>> wunder
>> K6WRU
>> CM87wj
>> http://observer.wunderwood.org/
>> 
>> On Sep 13, 2014, at 10:31 PM, Don Wilhelm <w3fpr at embarqmail.com> wrote:
>> 
>>> I failed to mention another point with regard to fan dipoles.  Do not mix 3rd harmonic radiators on
>> the same coax.  In other words, stay away from combinations of 40 meters and 15 meters, and also 40 meters and 30 meters.  They may work, but tuning problems are 'iffy'.
>>> 
>>> 73,
>>> Don W3FPR
>>> 
> -----------------------------------------------------------------------
> Bill Frantz        | Since the IBM Selectric, keyboards have gotten
> 408-356-8506       | steadily worse. Now we have touchscreen keyboards.
> www.pwpconsult.com | Can we make something even worse?
> 
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to wunder at wunderwood.org