[VHFcontesting] 6m, 2m, 70cm EME

[Ev Tupis]

 Hi Dave.  Thanks for the tip on the cavity filter.  I hadn't considered that.
With the assumption that KB7Q was pointing at the horizon, I calculate out...
9wl antenna at +20 dBi450 watts = 56 dBmPolarization "anomoly) = -3dB (equal V and H signal strength for you)
Ground Gain +3dB
Total approximate system ERP (coax loss unknown) for the QRP side = ~78 dBm
This is quite an education for me.  Thanks, Dave!
Ev, W2EV

    On Sunday, September 29, 2024 at 07:26:32 PM EDT, David Olean <k1whs at metrocast.net> wrote:  
 
 Hello Ev

I have been playing on 432 and 222 MHz of late. It seems that a power 
level of 100 watts will allow you some limited success on 432, but only 
with the most well equipped stations.  I would strongly suggest rapid 
polarity adjustments.  That is easy with a single long yagi.   The other 
suggestion would be to have a very good and selective front end. A big 
copper cavity in front of your preamp is probably needed if you are 
going to travel to different spots.  I can almost guarantee that strong 
digtal TV stations on the low end of the UHF TV band will kill most 
preamps. I have had serious trouble both on 222 and 432 that really 
compromised my hearing ability.  After the re packing of the UHF TV 
channels, there is probably a multi megawatt TV station nearby that will 
kill your 432 front end. The end result is that digital noise gets into 
the preamp and s/n ratios go South!

I tried today with KB7Q who was portable in Hawaii. I have a mid level 
station and had a bunch of trouble due to poor EME conditions.  I used 4 
X 12 el with polarity rotation.  Gene had a single  long yagi  (9wl) and 
450 watts.  Polarization was quite diffused much of the time, with V and 
H not being much different. It made Gene's signal very difficult to hear 
even with his 450 watts.  I am sure a better day would have been easier, 
but you have to realize that many days will be less than optimum.

I think 432 is your best bet with low power.  I have tried 100 watt QSOs 
on 222, but success is fleeting. I have done it with my four big yagis, 
but it is barely possible. I am sure that 144 is even worse unless you 
are talking about 2 or 3 "super stations". Good luck.

Dave K1WHS


On 9/27/2024 7:47 AM, Ev Tupis via VHFcontesting wrote:
> Of the 6, 2, and 70cm bands (those that are most likely to be in a modern HF+ radio), which band has been shown to support EME with the least overall ERP?  I'm thinking "portable EME" where it isn't possible to transport big antennas or a generator to have a kw amp. :-)
>
> Assume that this portable station would target QSOing with only the "top tier" of well equipped DX stations.
>
> I'd be interested in only recent experience rather than "back in the day". Also interested in both CW (human decode) and FTx (machine decode) modes.
> How little power and antenna (ERP) has been successful in making EME contact(s) and on what band/mode?
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