[amsat-bb] Moxon on top a Baofeng UV-5R for 70cm experiment

Pavel Milanes Costa co7wt at frcuba.co.cu
Tue Mar 17 00:05:41 UTC 2015

Hi to all.

Yesterday I was evaluating the construction of a small antenna for 
portable use on top of the Baofeng UV-5R... at the end I finished with 
two choices CJU vs moxon for 70cm handheld

After some modeling I choose the moxon over the CJU because:
- Smaller
- Less wire
- Less weight
- Less stress for the connector
- Just ~0.6 dB down vs the CJU
- By far better F/B ratio

After completion of the first "prototype"...

I successfully heard the CW beacon of Jugnu, CO-57, CO-58, PRISM and others.

The fire test will be tonight on SO-50, I know now I will copy ok, but 
the challenge is eliminate the desense of having two yaguis on a cross boom.

I will test the moxon handheld on RX (UHF) and a Jpole for the 2m uplink 
with 5W of a handheld.

I have not measured the SWR of the moxon, but with the simulation the 
measures are not "that critical" for getting a less than 1:2 of SWR over 
the entire 70cm band (1:3 bandwidth is about 16 Mhz)

The moxon "experiment" is just ~25 cm width and ~15 cm height (may be 
smaller also, the minimal height is ~10cm + connector) over the Baofeng 
UV-5R, there is no much stress on the connector.

I used a SMA to BNC adapter (the kind with a rim to fit tight to the 
radio body) and then a clamp on BNC (male) with a bronze tube as coaxial 
shield/boom of the antenna.

Wish me luck with the desense problem...


M.Sc. Pavel Milanes Costa, CO7WT
SYSOP Nodo Gateway CO9JAZ
Ciudad de Camagüey, Camagüey, Cuba.
Cell: (+53) 53-847819

More information about the AMSAT-BB mailing list