[Boatanchors] Modern AM Modulation techniques

[rbethman]

Hi All,

Solid State presents problems all over whether it is commercial or Ham.

There is an advantage that ham has over the commercial stations. We 
aren't having to stay on the air for 24/7 to make revenue.

Our "matchboxes" or "tuners" if you will, are a great deal less 
expensive than the commercial folks.

We also have the ability to use antennas such as Double Bazookas. They 
present a very broad bandwidth to the transmitter.  The one I obtained 
is indeed sold across the counter at Ham Radio Outlet. They need a balun 
right at the feed-point, and then 300ohm stubs on the end of the coax.  
I don't happen to possess a balun or two, nor the 300ohm line either.  
So for the first time in over two decades I bought an antenna in lieu of 
building one.  The 40 meter one presents a nominal 2:1 VSWR across the 
entirety of 40meters. My TS-2000 has a built-in antenna tuner for all 
the HF bands. Then the Amp Supply LK-500ZB is a pair of 3-500Zs that 
tune with its own PI network.  Either way I go, this antenna fits my 
needs just fine.  Otherwise, I am having great success with it on 40 meters.

(It went up in the middle of the night, about 1 AM if I recall 
correctly, and in the rain to boot.  I think it is a prescribed ethic 
for Amateur Operators to perform antenna work under adverse weather 
conditions!)

The only thing you have to decide is whether to mount it like an 
inverted "V" or horizontally.  This bears on the directive lobes of one 
over the other.

Regards, Bob - N0DGN
[ Old Sarge ]


On 10/5/2015 2:03 PM, Rob Atkinson wrote:
> Hi Jim,
>
> I don't know much at all about Class D.  The component problems I have
> heard of with the ham gear has to do with blown final FETs and I think
> the problem is guys running the rigs into vswr loads that are too
> high.  All of the class D rigs both ham and broadcast have to be on
> antenna systems where the rig is seeing no more than 1.2:1 vswr.  The
> broadcast rigs even have "antenna tuners" if I remember correctly.
> they have high vswr alarms that trip off the rigs if there is any
> excursion of line impedance.  I have heard all sorts of stories.
> Some stations back when they first went solid state, had to have their
> systems re-worked because they had towers with over 1.2:1 at the
> bandwidth edges.  An AM bc station takes up at least 20 kc.  They'd
> have a fine match at carrier frequency but trip off the rig when the
> sidebands went out far enough to encounter the bandwidth limit of the
> system.   The tube rigs didn't care.  I heard WSM in Nashville had a
> problem with birds hitting their unbalanced open wire line and
> tripping off the solid state rig when it was new.  The tube rig would
> keep going and fry the bird.  They had to go to a buried pressurized
> heliax line to solve the problem and keep the solid state rig happy.
> The class E rigs supposedly don't have this problem but I don't know
> anything about them.
>
> There's about 2 or 3 months every year in summer when solid state has
> minor appeal to me because the shack is just too dang hot for tubes,
> so I operate CW or tend to other matters.  The rest of the time I'll
> take filaments.
>
> 73
>
> Rob
> K5UJ
>
> On Mon, Oct 5, 2015 at 11:56 AM,  <w5jo at brightok.net> wrote:
>> Are those RF modules so expensive to preclude their use in Amateur
>> equipment?   The commercial digital AM stuff for Amateur radio seems to have component problems and using those modules might take care of the problem.