Re: mono band 2 meters rig based on the micro BITx circuit #ubitx #2meters

ajparent1/KB1GMX <kb1gmx@...>
 

For 6 and 2m SSB use it is a great staring point.  The power amp stages are not up to it for 2
at all but for 6 with work it can be made to work.    For the RX side you need a good LNA
on 6 and 2.  For 6 a gain of 10-17 db is enough. For 2M the gain will need to be closer to
20Db and the noise figure under 1 db.

To do dual band you need two front ends (LNAs) and switching from those to the 1st mixer.  Same for
the power out stages as wide band in that range is tougher to do than a per band stages.    A target
power of 10W is adequate 20 would be better.

For 4M we don't have that band here but that is about the same story as 6M however its going to
need a better power amp.  The IRF510 can pump power thee but everything before it has hit the
wall at 10M and needs better devices to go higher. 

UHF with ubitx its better to use it as an IF with a transverter.

As to VHF loop antennas, forget the Vacuum variable. its not needed.  For 6M the loop is about 30 inches
across and the end gap tunes it.  For 2M about 11inches and the end gap tunes that.  For VHF height is valuable
but also makes it hard to hide.  Gama fed in both cases.  Use good coax (quality RG8X minimum for short
(under 25ft) runs as losses are painful.  For longer runs RG8 .400 cable (RG213 or LMR400) are the usual.
However if you can do a beam (easy on 2M due to small size for a 4 element) it really helps.  Staced loops
also help but the stacking distance for 6m is around 12Ft and for 2M 4ft so its not stealth.

NOTES:
Around here in Eastern MA USA getting higher than the trees is the trick as they absorb a lot.   That is rarely
stealth.  Second best is higher than buildings.   Dead last is in the attic, roofing material especially wet are
absorbers.  Indoors works for local to a few miles at best.  I run 6M ssb from the mobile with a square loop
onthe truck using a HB rig at 4W or I add in the 6M brick I built to pump that up to about 70W.  The home
station the usual rig is HB contest radio for 6M (about 7W),  Tentec 6n2 (20W), and FT817 for  432mhz. 
Matching HB amps to get to 160W on 6,  160W on 2, and 60W on 432.  Antennas see QRZ, I have
5 elements on 6M, 11 elements for 2M and 15 for 432.  All are my design or highly modified commercial.
I also have antennas for Field Day (last full weekend in June) for 6/2/432 that are somewhat portable. 
Mountain (or high local hills) topping works using simple beams or loops.  Be aware unlike HF
polarisation counts, for SSB (VHF AND UHF) its generally horizontal here, the islands, and from
all accounts in Europe. cross polarization of direct local links incur great losses ( sometimes
more than 20DB).

I've been on VHF and up for a long time and built for all of the bands including 432 (transverter to 10M).
It is more home to me than HF.

Allison

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