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Pages: Prev 1 ... 5 6 7 8 9 [10]
 91 
 on: Today at 02:41:47 PM 
Started by KG9SF - Last post by KE4JOY
Yup, personal spat. About where I expected this to go.  Roll Eyes

 92 
 on: Today at 02:36:12 PM 
Started by AE5HL - Last post by WI4P
The FT-450 in all it's configurations is a good little radio but be aware the internal tuner will only tune about a 3:1 mismatch thus limiting you to resonant antennas unless you add an outboard tuner.  You can save some significant $$ by choosing a different Power supply such as Samlex SEC 1223 or similar.

 93 
 on: Today at 02:36:10 PM 
Started by 9A5BDP - Last post by G3RZP
2N5109  is specified for low noise and linearity in CATV applications. The 2N3866 was designed for Class C transmitters.

 94 
 on: Today at 02:34:09 PM 
Started by KB1WSY - Last post by G3RZP
Martin,

I think you are worrying too much about things that don't matter!

It's amateur radio, and I doubt I would worry even for a professional application!

String up some wire and get on the air!

Remember that "Perfection is the enemy of good enough".

 95 
 on: Today at 02:32:03 PM 
Started by VK4CH - Last post by N7SMI
Yep, being just 75km off the coast isn't even close the required 350km minimum requirement for new DXCC entities. It does look like a nice place though and you should have fun activating it.

 96 
 on: Today at 02:30:29 PM 
Started by WQUD444 - Last post by G3RZP
Any of the systems that basically work by measuring the return loss have problems as the return loss decreases. Back in 1984, the HP Journal had an article on how the return loss measurement affected accuracy, and showed a series of loci on a graph showing error as the load moved away from 50 ohms.

if you are running an SWR below 10 or 20;1, the antenna analyser is useful tool. If you are up at a few thousand ohms - an end fed half wave, accuracy is another matter.

Still, they didn't worry about SWR in the 1930s.....and still worked DX!

 97 
 on: Today at 02:23:27 PM 
Started by WD8VN - Last post by G3RZP
Do what David, WX7G, says.

 98 
 on: Today at 02:21:46 PM 
Started by K1YTG - Last post by G3RZP
Any single crystal filter with a phasing control had a variable frequency notch. The Q multiplier did suffer from problems with very strong adjacent channel signals. The Q" multiplier could not, in general, get up to the Q of the crystal - the math as to why is a bit complicated, though. Trying to (over) simplify, if you reduce the shunt negative resistance of a tuned circuit until it oscillates, you end up with a certain negative conductance. For a crystal, with its inherently higher Q, the shunt conductance needs to be lower or in other words, the Q is higher.

As the math books say 'it is left to the reader to produce a proof of this'!!! But basically it is that at the verge of oscillation, the Q would be higher with a crystal than with a tuned circuit. But it IS a damn sight cheaper!! Plus it is more repeatable with less playing around....

 99 
 on: Today at 02:11:34 PM 
Started by K1YTG - Last post by WA2CWA
Read this:
http://amfone.net/Amforum/index.php?topic=26052.0

Pete, wa2cwa

 100 
 on: Today at 02:11:07 PM 
Started by K8AXW - Last post by W5PFG
When you say "work the ISS," I ask "which mode?"

There are two primary ways to "work the ISS."

1. FM voice crew contact.  This is pretty rare these days.  The crew has other things to do for leisure.  They do it for special events and occasionally in their free time.  It uses 2m FM simplex, split channel.  It's workable with a modest omni antenna, but a 2m yagi (2-3 elements) would be better.

2. FM packet exchange with another terrestrial station. Essentially in this mode, you use the ISS as a packet digipeater.  2m FM, single channel.

www.issfanclub.com <- Make that your friendly site for ISS information.

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