Viking II Grid Drive on 10 meters

[w5gw]

With recent activity on 10 meters I decided to put my Viking II on 10 meters near 29 MHz where all the AM activity seems to congregate. 

Grid drive using a 7 MHz VFO or crystal was dismal. Suspect weak Osc and/or buffer tubes.

Since my VFO is a DDS2 from N3ZI, I decided to experiment.  Use of a GDO determined the Osc was resonant at 14.5 MHz thus the Osc and buffer are both acting as doublers to bring the 7 MHz VFO signal up to 29 MHz.  I fed in 14.5 MHz from my DDS2 and get plenty of drive now. The 6AU6 Osc sees a stronger signal and just acts as a fundamental amplifier instead of a doubler.  The buffer tube (6AQ5) sees a stronger drive and it is now very easy to get all the grid drive I need to the finals.

The DDS2 is a nice addition and easily built, but you do need a small amplifier (easily made) to get it's output up to 1-2 V RMS before feeding it into most vintage rigs.  Here is link to the VFO kit http://www.pongrance.com/super-dds.html

While I was experimenting I also put in a 6AH6 in the Osc and fed in my 7 MHz VFO signal.  That could also get me better drive, but I like the 14.5 feed as it is easier for me to double the VFO dial setting in my head to get the output frequency on 10.

[KX5JT]

True that it takes a bit more drive for the grid on 10 meters.  The Johnson 122 VFO works okay for me now that I repaired some bad joints in the buffer.  I guess we are too close for 10 meters but maybe I'll work you on another band sometime.  10 is really hot though!

[w5gw]

True that it takes a bit more drive for the grid on 10 meters.  The Johnson 122 VFO works okay for me now that I repaired some bad joints in the buffer.  I guess we are too close for 10 meters but maybe I'll work you on another band sometime.  10 is really hot though!

John,

I work 7.160 AM a lot in afternoon say from 2-4 PM local. I work some folks in Lake Charles as well as Mississippi so we should be able to close the link.

My other Viking II has the 122 VFO - its drive on 10 is anemic as well.  Time to find some better tubes. 

73

Gary - W5GW

[KB2WIG]

"My other Viking II has the 122 VFO - its drive on 10 is anemic as well.  Time to find some better tubes.  "

how old is the coax from the 122 to the VK2??  I kinda wonder if some new stuff may be better.

klc 

[KX5JT]

You can get 6AU6 tubes for 4 bucks shipped on ebay sometimes.  Maybe used but tested before shipped. It's nice to have a few of each tube on hand.

[w5gw]

"My other Viking II has the 122 VFO - its drive on 10 is anemic as well.  Time to find some better tubes.  "

how old is the coax from the 122 to the VK2??  I kinda wonder if some new stuff may be better.

klc 

An easier approach is to replace either the VFO's 6AU6 with a 6AH6 or the Osc in the Viking II with a 6AH6, or both.  You will get more output from the VFO and when the Osc has to act as a doubler it will do a better job than the 6AU6.

I doubt the coax will make that much of a difference.  Loss at 7 MHz for a couple of feet will be minimal.

[w5gw]

First contact on 10 meter AM today was G3UUR.  What a thrill to get the heavy iron up on 10. 

[KM1H]

Ive been using 6AH6's for years in my 122's and Viking I and II CDC, it certainly makes a difference and it works as well in the Globes. The II has been sort of stuck on 10M the past month, too much fun to QSY.

Carl