[AMRadio] W9INN antenna & Central Electronics 20A

[Gary Schafer]

Jim,

Some notes on the 20A.  It is common to be able to balance things and
get more side band suppression on one side band than the other. You need
to switch back and forth and find the point where both are about equal.
Don't expect more than 30 to 35 db of suppression. You may be able to
get in excess of 40 db on one side band with a single tone at 1 kc but
if you change the frequency of the tone you will find that the
suppression will drop. This is because of the audio phase shift network
not being able to maintain the proper phase shift over the full audio
range.

I have found it best and easiest to align the side band suppression by
talking into the mike or with a long ooooh and listening on the opposite
side band with a receiver. This seems to let you balance things better
over the speech range than a single tone lets you. It is also easier if
you have a little audio hum (common on all 20A's).

As for the GSB201 amp, you will need a good 100 watts to drive it to
full power. A single 811A in grounded grid will not get you enough power
behind the 20A. I have run a pair of modified 1625's and 4 1625,s (also
837's) in grounded grid as a driver. That is marginal. It takes around
1000 volts or better on the 1625,s to get much power out. Then you will
have a job getting 100 watts out. On 80 meters and maybe 20. On the
other bands the 20A has less drive.

I have a pair of 1625's now that I drive the grids with the 20A. This
works pretty good and is much better than the grounded grid
configuration as far as getting enough power out. With the 1625's you
will need to run them in AB2 and have regulated bias voltage. If you run
them in AB1 they will not put out very much power. Only about 60 watts
for a pair in AB1.
I am in the process of building the same amp with a pair of 6146's grid
driven. This will be able to run AB1 and get over 100 watts out.  I
found that by making a small 4:1 balun and loading the grid with a
resistor I could drive it with no grid tuning. Simplifies the amp.
By the way my 1625 amp is built in an old ARC5 chassis.

73
Gary  K4FMX


jcandela at prodigy.net wrote:

> Jeff,
>
>     My "Stealth" antenna is down right now. I want to
> put up a shortened 80 meter dipole (maybe 60' long),
> such as a W9INN. Anybody use one? It would fit in my
> lot without a big visual signiture. I do not need much
> bandwidth.
>     I have been tinkering away restoring, and
> modifying a Central electronics 20A which I plan to
> use as an all mode exciter. Between broken circuits,
> mis-wired circuits, out of tolerance parts, etc. and
> out of date technology, I have under taken a large
> task. It required no less then fixing 5 items to make
> the balanced modulator stable.
>
>     I found a way to keep it from going from AM to DSB
> Reduced Carrier on voice peaks. When that happens, the
> signal really sounds lousy on a AM detector. I am
> still perfecting that. Can run 3 watts out now on AM,
> and modulate upward ~ 150% while still sounding good
> in my monitor (AR-88).
>     Currently I am fighting the SB suppression when
> switching between upper, and lower SB. I can
> compromise the settings for ~ 40 db suppression, or
> optimize one SB only for maybe ~ 55 db suppression.
> Looks like a lot of work to get both side bands right.
> Anybody play with this? CE uses 1N34A's (X4) in the
> balanced modulator. Anybody know of something more
> modern, maybe hot carrier diodes (4) in a single
> package? Sorry for mentioning SSB on a AM forum. I am
> however intending to run AM primarily, and Hi-Fi SSB
> when necessary.
>
>     I have a linear (Gonset GSB201)but it is GG, and
> requires ~ 70 watts pep input for full output. I am
> thinking of using a "one lunger" 811 GG mounted in a
> arc-5 chassis to fill the gap from my 20a output (15-
> 20 watts pep)to ~ maybe 100 watts pep. I have a "near
> perfect" 80 meter arc-5 that I hate to tear up. Anyone
> got a beat up one lying around? Need chassis, covers,
> and no tubes, or roller inductor.
>
> Regards,
> Jim
> Wd5JKO
> --- Original Message ---
> From: "Jeff/W5OMR" <w5omr at yahoo.com>
> To: <amradio at mailman.qth.net>
> Subject: Re: [AMRadio] Info regarding John, W5MEU
>
> >When do we get to hear WD5JKO on the air again, Jim?
> >
> >:     Jeff,
> >:
>
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