[AMRadio] New to AM

[Geoff Edmonson]

  On 12/29/2010 02:01 PM, Jerry Colton wrote:
> Thanks Bob (N0DGN)..... Your comment has made me feel much better! hi hi
> Thanks again all
> Jerry - N1TKO
> PS - Just from the emails I have received, I can write an "AM How To" book
>

Jerry, my new friend, we've not even scratched the surface! ;-)

There's some ol' joke going around, that if you ask an AM'er what time 
it is, not only will you get the time, but it'll be -after- you've been 
imparted with the knowledge of how to BUILD that clock, too! ;-)

Welcome aboard!

Just an FYI... I run a solid state rig mobile (as I live in an apartment 
and antennas are a no-no).  It's a Kenwood TS-450SAT.  I don't use the 
Antenna tuner (misnomer - they're "impedance matching devices") because 
I operate into a resonant antenna.  My antenna is a bug-catcher.  
Between the antenna and the transceiver, there are two devices; an SWR 
bridge and a (4) 2SC2879 amplifier that produces around 600w output.

With the amp -off-, I use the transceiver to determine where the 
resonant point of the antenna is, with the SWR bridge.  Once the antenna 
is tapped, and the impedance matching coil is set and minimum SWR is 
achieved (which isn't exactly maximum field strength, but hey - we're 
talking Solid State stuff here) then I kick on the amp.

Remember Darrell/WA5VGO's comment about (4) 811's only giving you ~150w 
out?  That's because the total output of the device is in the 
neighborhood of 600w.  Using Low Level Modulation (ie: non-plate 
modulated tubes) the carrier level shouldn't be more than 1/4 of 
whatever the total output of the amp is, in order to preserve linearity 
in the AM mode.  PEP output @ 100% modulation = Carrier x 4 (typically).

My TS-450 has both a Power control as well as a Carrier control.  The 
rig is cut back to 50w out, max.  This gives me 12.5w maximum carrier I 
could use.  Luckily, the amp doesn't need that much to make full output!

  I leave the Power turned all the way up (so that all of it's output 
power can be used, and not 'limited' then I only crank up the carrier 
level while in AM, to produce ~125 to 150w of carrier and then modulate 
the rig until I -just barely- see the meter move slightly upwards.  That 
procedure has garnered some fairly decent reports.  It's not 
-excellent-, mind you ... not like a pair of 250TH's being modulated by 
a pair, or a single 833 modulated by a pair, or a pair of 250TH's 
modulated by (4) 813's in push-pull parallel... but, it -does- get the 
signal out there, and the high Q of the bug catcher makes it fairly 
copyable, so I'm told.

If I can achieve THOSE kinds of remarks from a -mobile- setup, imagine 
what you could do with a 60' tall full-sized 75m antenna and 100~120w of 
plate modulated RF?

Besides, the difference between 100w and 150w (if you wanted to use an 
amp behind the Apache) is negligible.  You have to go from 50 to 100 to 
get 3db of increase and then from 100 to 200 to get 3 more db, then from 
200 to 400 to get 3 more db.  50w to 400w is around 9db, and since 
S-meters are -usually- marked off in (around about) approx 6db per 
S-unit, you've only increased the meter on the far end from S-5 to S-6.5 
(roughly) for a 350w increase in power.  So, you can see how going from 
100 to 150w is like spitting in the Ocean.

It's a great service, Amateur Radio and a small niche like AM is a 
-great- thing to get into, if you're the technically minded type.

To me, that's where Ham Radio lost it's luster... nobody wants to build 
anymore.  Anyone can go to the local candy store, buy a rig, buy an 
antenna, put 'em up and get on the air and say "I'm a Ham!"  Well.. just 
because you can click a microphone button, doesn't automatically mean 
you know what you're talking about.  REAL RADIO, In my opinion, is 
building your own transmitter and/or receiver ... something you made 
with your hands, using the knowledge of electronics to coerce a bunch of 
electrons to either produce information through the form of a speaker, 
or impart knowledge and camaraderie amongst like-minded individuals (in 
our case, 95% of 'em are using the AM mode).

Welcome aboard, Jerry!  Hope the conditions are good some night, and we 
get to work.

73 = Best Regards,
-Geoff/W5OMR
(/m Baja Spring, TX)