[amsat-bb] Re: look this dual band egg

[K5OE@xxxxxxx]

Hello Ralph,
Hector, XE2EKY forwarded your posting to me.  

I have done some casual testing of exactly the scenario you proposed:  using a 2 m Texas Potato Masher II, which is really an eggbeater variant/derivation designed to add directional gain to the fundamental eggbeater design (see either the TPM II at http://members.aol.com/k5oejerry/tpm2.htm or the Egg II at http://members.aol.com/k5oejerry/eggbeater2.htm) on both 2m and 70 cm.  Please note there was not a second antenna built inside the first, as I used the 2 m driven element as a common feedpoint.  I found the antenna was, as expected for an odd-wavelength design, resonant at 70 cm also.  What I noted, however, was the pattern was not nearly as directional as the TPM II, but did have some F/B (I did not attempt to measure it, but would estimate it over 3 dB--about 1/3 of the TPM II at it's design frequency).  Specifically, my setup was a dual-band mobile rig (FT-5100) operating AO-27.

What occured to me at the time was that if a second reflector, tuned for 70 cm, was added to the antenna, it was very likely to perform quite well, especially for a dual band rig that already had a built-in duplexer.  The interesting modeling options would be to see if a 1/2 wl reflector was effective or if a 3/2 wl reflector would be required (since the driven element is 3 wl at 70 cm).

I hope this is helpful and gives you some ideas for experimenting.  Please let me know how it all turns out.
73,
Jerry, UA3T/K5OE


 > One of the ways that I have tried to economize when it comes to satellites
 > is by constructing my own antennas.  I currently have two quagies which I
 > built from the Antenna Handbook and I am looking forward to getting them
 > back up on the roof and on the air.
 > 
 > I have been trying to research and investigate more portable antenna systems
 > than my 12 - 15 foot quagies (for Field Day and other uses). I have read
 > various things about egg beaters here and I have a question for the group.
 > I have received information from a tech support person at M2, and I am
 > interested in other opinions & experiences.
 > 
 > Specifically, has anyone experimented with a dual band (144/432) eggbeater?
 > Considering that 144 and 432 are exact multiples of each other, will a 2M
 > eggbeater resonate at 432?  If you built a 432 eggbeater inside a 144
 > version, would the 432 pattern be significantly degraded?
 > 
 > Any and all discussion would be greatly appreciated.  It's time to start
 > preparing and experimenting for this years Field Day effort.
 > 
 > Thanks very much in advance - 73,
 > 
 > Ralph G. Sbragia, CSP, CHST
 > Board Certified Safety Professional
 > KD6FYT
 > kd6fyt@ocraces.net
 > http://users.deltanet.com/~sbragiar/safetymain.htm
 > 
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