[NLRS] Advice on 2M transverter, bricks

[John P. Toscano]

Cathy James wrote:

> eHam has very mixed reviews of the Down East Microwave 60W 2M 
> transverter.  Elecraft's XV144 has superb reviews, but is only 20W.  I 
> think the prices are similar.

I'm surprised at the negative eHam.net reviews of the Down East 
Microwave model.  I don't own that particular model, but have their 
transverters for 222, 902, 1296, 2304, 3456, and 10368, and have been 
very well satisfied with all of them.

My 222 transverter uses the old-style cast aluminum box like the 144 
model. It seems to be "bulletproof", and I'm shocked that one reviewer 
had so much trouble with his 144 transverter.  Yeah, the box looks a bit 
ugly, and the wiring inside is a bit messy, especially compared to the 
newer microwave models with their extruded aluminum cases, but the thing 
works, and works well.  When I say that my 222 transverter is robust, I 
speak from experience.  Due to a bonehead mistake on my part, during 
early testing, I accidentally dumped a full 100 watts into the 
transverter instead of the milliwatt-level input it is designed for. I 
cooked the 50 ohm resistor across the input, but a quick foray into my 
parts bin for a replacement resistor got me going again with no evidence 
that the transverter was any worse for the experience.  Later in 
testing, I hooked the output to a SWR/Wattmeter and dummy load, and kept 
getting zero watts measured.  It finally dawned on me that something was 
amiss when I brushed my hand against the heat sink and found it to be 
quite hot. The unit was making lots of power, but none of it was getting 
to the meter. It turned out that the coax jumper between the transverter 
and the wattmeter was shorted, and the transverter had been dumping its 
full power into zero ohms.  Again, after replacing the cable with a good 
one, the unit has performed flawlessly ever since.

> For those of you who do moderately serious weak-signal CW and SSB work 
> with a 3-element beam or less, what power do you find to be necessary?  
> Will I need a brick behind the XV144 if I go that route?  What are some 
> models of brick that are affordable and _readily available_?  I'm not 
> interested in purchasing anything off of eBay or spending a year 
> prowling hamfests hoping to find a particular model.

I think you'll be much happier with something in the 100-200 watt 
neighborhood.  One of my 2M radios only puts out 20 watts, and I found 
that to be clearly too little for any serious SSB work.  I generally run 
it through an RF Concepts brick that boosts it to about 150 watts, and I 
am very comfortable with this level.  My other radio will put out 50 
watts on 2M, and I've run it "barefoot" this way at Field Day with fair 
success.  I did this to keep things simple, because the output of this 
radio is much too high for the input of the 2M brick, and I was afraid 
of failing to dial down the power when switching to 2M from another band 
where full power was being used, especially when a guest operator was 
using it.  I worked everyone I heard, but it sure wasn't as busy on 2M 
during Field Day as during a VHF+ contest. As far as affordable, quality 
bricks go, I am at a loss. The only thing that seems to be readily 
available is the MFJ series, and I have heard mostly bad things about 
them.  TE Systems bricks are harder to find, and they apparently work 
well, but if/when they break, they are extremely difficult to get 
repaired. I, too, would be interested to hear of other options that 
folks like.  I have a matched trio of RF Concepts amps for 144, 222, and 
432, which have been very good to me, but they are no longer made or 
supported, and seldom turn up on the used market.

> I would probably experiment with both my Uniden HR2600 and K2 to see how 
> much difference the receiver makes.  I presume that I need to build the 
> XV60 interface for the K2 to do this?

In spite of my comments "defending" the DEMI transverter, I expect that 
the K2 is such a superior radio to the HR2600 that you would do best to 
go with the Elecraft transverter that is designed to fit it. Sure, the 
DEMI model could be made to work, but every once in a while I like to 
take the easy way out.

> I'm currently building a 3-element quad from PVC and copper tubing, and 
> hoping to get within sight of the theoretical gain for this design (9 
> dB+).  Is this a reasonable gain figure for weak-signal, or am I going 
> to find that everyone else is running 5 or 6 element beams?

KB0LYL has used a cubical quad antenna on 2M for a long time, and has 
racked up some record scores on the 2M band in the ARRL VHF contests. I 
would bet that his antenna is longer than 3 elements, however.

I have used an ancient 10-element Cush Craft beam rescued from the scrap 
heap (a ham was taking down his tower and giving away or throwing away 
all the antennas, so I grabbed it along with a few others).  It has 
served me quite well. I do plan to replace it with a stacked pair of M 
Squared 2M12 antennas (12.8 dBd each, about 15.8 dBd stacked), but never 
seem to find the time to do the tower work necessary to get them up in 
the air.  I have used a single 2M12 many times in portable operations 
(Field Day, and in a multi-op portable setting) and been extremely 
pleased with its performance. I really look forward to having a pair of 
them working together!

Having said all that, I must also admit that I've done a little 
contesting with nothing more than a stacked pair of M Squared SQLoop 
antennas, the predecessor of the HOLoop that they currently sell.  Yeah, 
I really notice the loss of gain compared to my 10-el CushCraft, but 
they come in handy when the rotator is busted or if I want to quickly 
hear in a direction that the main antenna is not pointed at. In case 
you're not famililar with them, they are a horizontally polarized 
omnidirectional loop antenna.

> Are many weak-signal ops running CW, or is most of the operation SSB 
> these days?  I think CW will be much easier than SSB if I'm not running 
> a mega-power station with a 50 foot beam...

At least during a contest, what I have found is that most operators use 
SSB, but you need to be prepared to use CW if there's a weak one that 
you can't make the QSO with on SSB.  Having some CW skill is a very 
definite plus. My very poor CW skills have saved a significant number of 
contacts that otherwise would not have happened. (Someday, when I stop 
working insane hours, I'll get some time to PRACTICE my CW skills and 
bring them up to a more acceptable level. I definitely have the DESIRE 
to learn and the ABILITY to learn better CW, all I need is the TIME.)

Hope that helps. I look forward to hearing you on the air in a future 
contest, or whenever!

73 de WØJT