[NLRS] VHF Amplifiers Legal limit Digital -

Wed Feb 3 16:21:25 EST 2021

 Hello Rich and all - The following are lessons learned running digital at legal limit for contests ( I've ran Digital for hours and hours and hours NONSTOP ) .... first , I run my xcvrs always with the rx seperated from the transmit line to facilitate SAFE operation with a very low noise preamp AT THE ANTENNA . Second , when I build up a tube amp for operating , I keep in mind that I will use it for digital operations AND I use components that the values and ratings are for TWICE or three times that needed at 1.5 kw ( yes the 2 meter GS35 amp at the farm will run 3kw + but I dont trust my T/R relay at that level ) Another thing to remember is the FT991 WILL DRIFT WHEN THE INTERNAL COOLING FAN KICKS ON - it pulls air across the local oscillators that cause it ( wont bother on 6m BUT DOES ON 2 AND 432 ) When you have drift , you lose a signal decode on either end of the QSO ( software cant handle it - mainly affecting your 2 meter meteour scatter QSO rate and EME JT65b, etc ) . This is documented online AND I hooked both the FT991 and the TS2000X to seperate computers and dummy loads and have confirmed this !!On the FT991 , I have an extra cooling fan that I piggy back on top of the factory fan to pull air out and on the TS2000X , I did a fan mod that has the fan run at 50% speed all the time - Running digital modes , the long duty cycle is your enemy - always run fans 100% of the time . If you dont compensate for the extra heat due to the longgggg duty cycle , you will end up having something go wrong right when you dont want it !! ( i.e. - like the original balun box on a cushcraft 17B2 actually catching on fire due to the heat build up from corrosion while doing 144 EME ) Anyway , whatever your amplifier choice is Rich , compensate for the extra duty cycle associated with contesting using digital . Good luck and Happy DXing !!Any questions , feel free to email me - Ron KA0RYT 
     On Wednesday, February 3, 2021, 01:52:42 PM CST, Rich Westerberg <richn0hjz at gmail.com> wrote:  

 Hi Jon -

For now I'm in the 3-band category.  With no preamps and no 432 antenna, I
still managed 6th place in the US in the category last June.  If I can get
decent antennas up, I'll be in a better spot.

I'm looking to get at least 200 watts for 2M but could go higher for 6 &
2.  If that requires 22v, then I'll work to get that.  Since things are so
tied to digital, I just wanted to be sure I got an amp that wouldn't melt.
I'm looking at a few fronts.  Just looking for recommendations (solid state
bricks or larger).

Rich

On Wed, Feb 3, 2021 at 11:24 AM Jon Platt via NLRS <nlrs at mailman.qth.net>
wrote:

> Thoughts on VHF amplifiers:
> For general operating, more power is always better than less power.
> For contesting though, there are rules.  For the three ARRL contest, the
> SOLP is 200w PEP or less on 6 and 2m, 100w PEP or less on 222 and 432 MHz,
> and 50w PEP or less on 902 and above.  If you are over these power limits
> on any one band then you fall into SOHP category.  The ARRL contests also
> has a SO 3 band category in which you would be limited to 100w PEP or less
> on 50 and 144 MHz, and 50w PEP or less on 432 MHZ; just these three bands.
> The current ARRL rules do not make a power limit distinction for multi-op
> or multi-op limited as both can run legal power; there is no low power
> multi-op category, just "multi-op".  For CQWW VHF, which is just 6m and
> 2m, there is no power classifications except for SO QRP which limits you to
> 10 watts or less on all bands.
> Your FT991 provides 100 watts on 6m and 50 watts on 2 and 432.  That alone
> puts you in good grace for SO3B with full allowed power on 6m and 432, and
> only 3 dB down on 2m.  If you wanted to, you could look for a solid state
> 2m amp that gets you up to 100 watts but its of questionable value. ..If
> you want to jump into the SOLP category you have some room there to go from
> 100 to 200 watts on 6m (3db), 50 to 200 watts on 2m (6dB), and 50 to 100
> watts on 432 (3 dB).  Again, adding a solid state 2m amp at first may be
> the best value as that gets you close to 6 dB of gain on that band.  If you
> enter the SOLP category you would be competing with other SOLP stations
> that may have more bands.  Adding those more bands gets to be more work,
> more cost, etc, but sure is a lot of fun !  Note that the ARRL's Limited
> Multi-op is any four bands (or less).  ..If you want to go big, especially
> for say CQWW VHF and the June contests, go for high power on 6 and 2m.  One
> consideration for you would be the availability of 110VAC vs 220VAC when
> adding a high power amplifier.  Lots of guys are having fun now days
> running such high power and using all sorts of modes, including digital, to
> work lots of stuff.  ..So, to summarize my random thoughts, you are
> probably well suited right now to jump in with a competitive SO3B station
> with the FT991.  Improvement after that may be to add a 2m 200w solid
> state amplifier (?) to either run it at 100 watts for SO3B or full power
> for SOLP.  Given that you have lots of 2m drive (i.e. 50w), you can go
> with something like a Mirage B-320-G, 50w in give 200w out.  After this,
> the return on investment dwindles unless your thinking about going
> truly high power in which case you may need 220VAC, I defer to others on
> that subject.
> I await to see what others may think...73, Jon  W0ZQ
>
> ______________________________________________________________
> NLRS mailing list
> Home: http://mailman.qth.net/mailman/listinfo/nlrs
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:NLRS at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
______________________________________________________________
NLRS mailing list
Home: http://mailman.qth.net/mailman/listinfo/nlrs
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:NLRS at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html