[TowerTalk] 80m 4Square Comtek box

[Jan Erik Holm]

Jim I agree however if you see it from a Swedes perspective
it will come out totaly different.
Those 350 dollars probably looks more like 900 dollars to
me in Sweden.
Hope you understand so I don´t have to explain it further.

73 Jim SM2EKM
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Jim Lux wrote:

> At 02:23 PM 11/18/2004 -0500, Tom Rauch wrote:
> 
>> > Actually, there is enough information in ON4UN's book for
>> a
>> > competent individual to build a hybrid style (quadrature)
>> > phasing unit without much more than an MFJ-259B.  Of
>> course
>> > a good scope and current probes would help if one wanted
>> to
>> > optimize the unit.
>>
>> By the time most people did all that, they would be better
>> off just buying the Comtek. Retail parts aren't cheap or
>> easy any longer.
> 
> 
> 
> I'll second that...
> Let's see..
> 
> Knowing the values is easy.  for 50 ohms, 3.8MHz, you want L=2.09 uH, 
> C=419pF
> The schematic is simple, too.
> 
> Then, you can engage in a few hours of design time to find an 
> appropriate core and design the inductor. (remember, it has to handle a 
> kilowatt)
> The caps are catalog parts (although you need to make sure they have the 
> right current ratings, etc.), so it won't take long to find them.
> Then, you'll need to select some appropriate relays, a decidely 
> non-trivial process, since RF relays that handle a kilowatt are quite 
> pricey, so you're going to want to use some other kind.
> 
> Order everything (after rummaging through the junk box) you need.
> 
> I'd wag the parts cost at around $100-200 (but it could easily be 
> more... suitable non-surplus relays are probably $10 each in the 
> catalog, the caps will be fairly inexpensive, cores are a couple bucks, 
> but you have to consider things like enclosures, connectors, etc.)
> 
> Wait 2 weeks (because you can't really work on it during the week).
> 
> Now, spend some time winding that inductor, figuring out how to assemble 
> it, put it into a box, etc.  It's probably a nice 2 day job.  And, if 
> you have the time and tools, it would be enjoyable.. a nice combination 
> of mechanical engineering and electronics.
> 
> But all the same, if you paid yourself something like $8/hr, you'd 
> probably spend 20 hours on the whole project, so the labor cost is $160.
> That's a pretty unrealistic labor cost.  Either you have the time to 
> spend on it, in which case the time is free, or you're busy with lots of 
> other things, in which case the time is infinitely expensive.
> 
> Hmm.. or, just buy the Comtek box for $350.  Not a bad deal.
>