[AMRadio] DX-100B Low Output on 15 and 10 Meters

John Coleman, ARS WA5BXO wa5bxo at pctechref.com
Mon Oct 18 09:41:03 EDT 2004

The DX100 uses a VFO running on 7 mhz for the upper bands and the same
multipliers stages, just different coils.  Harmonic multiplication of
frequency becomes inefficient as the multiplication is increased (less
energy in the harmonics) so this means less output from each stage.  You
will probably notice that the drivers and buffers run much hotter on 15
and 10 meters.  More drive from the VFO and other stages will generate
higher energy in the harmonics so this could help a lot if you're in to
modifications (maybe extra stages of buffering and some extra switches
and holes).  Higher Q circuits help a lot too.

John, WA5BXO


-----Original Message-----
From: amradio-bounces at mailman.qth.net
[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Mark Bell
Sent: Sunday, October 17, 2004 9:12 PM
To: AM List
Subject: [AMRadio] DX-100B Low Output on 15 and 10 Meters

Folks --

I'm getting low output on 10 and 15 Meters.  Typical output on the other
lower bands is well over 100 Watts.

All tubes test good, and I re-did the Buffer Coil adjustments as per the

After tune up on 15 Meters, here's my readings:

Driver current is at 6 ma
Ig is at 2 ma
Ip is 250 ma
Output power 50 W

After tune up on 10 Meters, my readings are:

Driver current is at 6 ma
Ig is at 2 ma
Ip is 250 ma
Output power 65 W

As a reference, after tune up on 20 meters, my readings are

Driver current is at 6 ma
Ig is at 6.5 ma
Ip is 250 ma
Output power 130 W

Just for "fun",  on both 15 and 10,  I upped the driver current to max,
which was 10 and 7 mA respectively.  The respecitve Ig's were 10+ and 5
and the output power (both bands) jumped to 80W.

So, seems I have a problem with the grid current on 10 and 15 M.  I
I'd start looking at the circuit around the Driver section of the
bandswitch.   I was wondering, though, is this a known problem with the
DX-100B that might be attributed to (perhaps) neutralization?

Any and all comments welcome.

Thanks & 73

Mark K3MSB

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