Gates VanGuard transmitter

[WA3OPY]

We have been asked to re-crystal a dual crystal oscillator in a Gates VanGuard transmitter.
The oven module is from NEL and is a 115 V unit. The temp controlled transistor oscillator is 14 V. It has an octal socket.
We do not have schematics for the unit and that is what we are trying to obtain; specifically which connections the octal socket go to.

Darell Brehm - WA3OPY
Engineering Manager - ICM
www.icmfg.com

[WBear2GCR]

Someone may know, or have the manual.

But I would think that on the customer side, someone could simply look at the socket and make that determination?

Also, I would think that the actual xtals in the oven are large size xtals.
Do you grind your own xtals there?

If not, a modification to the oscillator might be in order so that a smaller lower current
xtal might be used.

Thinking out loud, I have no actual information on this.

                              _-_-

[Ralph W3GL]

Someone may know, or have the manual.

But I would think that on the customer side, someone could simply look at the socket and make that determination?

Also, I would think that the actual xtals in the oven are large size xtals.
Do you grind your own xtals there?

If not, a modification to the oscillator might be in order so that a smaller lower current
xtal might be used.

Thinking out loud, I have no actual information on this.

                              _-_-

Bear,

Sometimes you really stick your foot in it...

Check out the web site he quoted, it should answer most of
your thoughts.  Sometimes it's best to think silently...
 

[Todd, KA1KAQ]

You're too generous, Ralphie. 

Darrell, there's a member here who actually owns one of these transmitters and I think he's been completely through it, so he should be pretty fluent. That's Mike/W8BAC. He travels a lot for work but if you can't find the answer you need, I'd suggest sending him a private message here.

[Mike/W8BAC]

Hi Todd and all. I keyed in on this first thing this morning. I dug out my manual but the schematic I have dose not include the exciter section, just the main frame amplifier components. I'll look again tomorrow but I think I sent the second manual to another CE needing help. Again, I'll look to see if I have his contact information as well.

Mike

[WBear2GCR]

Just because a company sells or advertises crystals, doesn't mean that they actually
make them in a factory on site - especially these days. Also, it does not mean that they
also still maintain the ability to make what are now antique xtal blanks and sizes. Today almost everything is small and low voltage. Which is why I made the comment... sorry if I was not up to speed on what ICM does.

I'd still say that it makes sense today to consider dropping in a revamped oscillator circuit that uses a smaller, lower current xtal. One could drop in a small solid state oscillator circuit and use the old oscillator tube as a follower or amplifier... or not.

But thanks for jumping on me with both feet fellows...

                      _-_-

[Ralph W3GL]

Hey Bear,

First, ICM has been in the crystal manufacturing business for several
decades supplying close tolerance units to commercial manufactures
and usually has the specs for the item on file for their products. 
 
From the tone of the original post, the poster is looking for info on
part of a FCC Type Accepted Broadcast Transmitter...

ICM supplies crystals ground to and burned-in (to meet the specified
tolerances required) so they need the full data on the original type
approved system.  

They do not make changes to this type hardware still in commercial
service.  

The poster did not mention the customer and the transmitter type
mentioned is still in commercial service at many BC Stations so it is
assumed his request for the information is not for some hammy hambone
modification to amateur frequencies....

Of course, this forum is basically aimed at amateur AM operators so it
would figure there just might be some AM hams involved with the broad-
cast  service, hence Darell, WA3OPY, probably figured (correctly) someone
here just might have the info he needs to complete the material requested.

Sorry I came on a bit strong but as I said, sometimes it's  best to think
silently for a while and observe before going public...  Believe me, this is
the voice of many years of experience  

 

[W7TFO]

the transmitter type mentioned is still in commercial service at many BC Stations

A vanguard still in BC service would be a real treat today....

73DG

[KA2DZT]

You tell'em Ralph.

Nowadays, most bears, when spotted, are rounded up and relocated.

Fred

[W7TFO]

I hope the OP gets the dope he needs.

I hope Fred and Smokey never cross paths...

73DG

[WBear2GCR]

Ralph,

You may be correct about the FCC requirements... unclear to me that changing out the xtal oscillator makes the transmitter no longer approved to run under the commercial license. Possibly so. Also it's unclear that this is not for a ham who has this vintage xmiter.

Regardless, my comments were pretty harmless, even if off base as it seems to turn out.
Only trying to help out.

So maybe a PM would have been a more appropriate way to give a heads up?

Perhaps you and some others are unaware that a substantial number of former contributors to this forum have left, gone, not to return because of getting "blasted" in one way or another. If there is no room for errors, foolish thoughts and comments, and mistakes, and only "expert" advice and comments, then we can move quickly to a one way format: "ask the experts".

I say if you can't roll with it, enjoy yourself, and have some fun, then what is the point at all in having a forum for people to participate in?

</soapbox>

                       _-_-

[W7TFO]

+1 Bear.

73DG

[KA2DZT]

Bear,

Your comments are always welcome.

Don't let Ralph rattle your cage.

We do get some bears occasionally wandering by in this area.  They do round them up and relocate them to deeper wooded areas.

Fred

[KD0HUX]

Ralph,

You may be correct about the FCC requirements... unclear to me that changing out the xtal oscillator makes the transmitter no longer approved to run under the commercial license. Possibly so. Also it's unclear that this is not for a ham who has this vintage xmiter.

Regardless, my comments were pretty harmless, even if off base as it seems to turn out.
Only trying to help out.

So maybe a PM would have been a more appropriate way to give a heads up?

Perhaps you and some others are unaware that a substantial number of former contributors to this forum have left, gone, not to return because of getting "blasted" in one way or another. If there is no room for errors, foolish thoughts and comments, and mistakes, and only "expert" advice and comments, then we can move quickly to a one way format: "ask the experts".

I say if you can't roll with it, enjoy yourself, and have some fun, then what is the point at all in having a forum for people to participate in?

</soapbox>

                       _-_-

[wd9ive]

Ralph,

You may be correct about the FCC requirements... unclear to me that changing out the xtal oscillator makes the transmitter no longer approved to run under the commercial license. Possibly so. Also it's unclear that this is not for a ham who has this vintage xmiter.

Regardless, my comments were pretty harmless, even if off base as it seems to turn out.
Only trying to help out.

So maybe a PM would have been a more appropriate way to give a heads up?

Perhaps you and some others are unaware that a substantial number of former contributors to this forum have left, gone, not to return because of getting "blasted" in one way or another. If there is no room for errors, foolish thoughts and comments, and mistakes, and only "expert" advice and comments, then we can move quickly to a one way format: "ask the experts".

I say if you can't roll with it, enjoy yourself, and have some fun, then what is the point at all in having a forum for people to participate in?

</soapbox>

                       _-_-

[Pete, WA2CWA]

[Todd, KA1KAQ]

Perhaps you and some others are unaware that a substantial number of former contributors to this forum have left, gone, not to return because of getting "blasted" in one way or another.

More rumor than truth. I've never seen anyone get 'blasted' here. Closest I ever saw was when Gary actually called out a long time member for making a clearly stupid post, and rightly so. Aside from a few bad eggs being shown the door, it just doesn't happen. Unless you're so thin-skinned that you take exception to someone disagreeing with you or calling you out for inaccurate/unsubstantiated information. Or you get offended when your endless garbage posts that have zero to do with radio muchless AM get dumped, or your trolling attempts get shut down. If that's the case, you're definitely better off somewhere other than here. We're not running an AOL chat room, after all.

The membership continues to grow daily with more and more participation from folks around the country and world, and the signal-to-noise ratio with respect to posting continues to improve. Not the kind of thing that happens if a 'substantial number' of good, contributing members are leaving. The crew must be doing something right.
 
Which is why you can come to the Tech section here and find not only info or ideas about a somewhat esoteric transmitter like the Gates Vanguard, you can also find folks who have used, maintained, or even own one. The depth and breadth of knowledge and experience here is second to none, and a direct testament to the quality and character of the membership overall.

BTW, Ralphie forgets more in a night than you or I will ever know and has a well-calibrated BS Detector as a result. I don't blame him for having high expectations or getting a little cranky at times.  

[Mike/W8BAC]

Hi Darell,

I found the schematics your looking for. I sent PDF scans to the email address you have linked to this reflector. Have a look and let me know if they help.

Mike
W8BAC

[k9qi]

Hello,

If someone is considering using this rig as their main (in the AM broadcast service), I would say, "Don't do it".  It is penny-wise, and dollar-foolish. As a back-up, maybe.   

I also own a Gates Vangard.  Retuned it from 680 to 740kHz about 23 years ago.  Pulled it form service 21 years ago.  It is now on 75meters (once in a great while) but will probably move to 160m.  The exciter in that rig is not very good.  It relies on a lot of feedback (close to 20dB if I remember correctly) to reduce distortion but, worse than that, the modulator is a diode across a tank circuit - the diode conduction varies the amplitude of the RF, later amplified by a single transistor, to drive the PA (which is a 4CX3000A operating Class AB1).  The feedback, although from the PA back to the audio input stage, actually reduces distortion from the low level modulator more than anything else.  That diode is not only an amplitude modulator, but, the varactor action of the diode, also generates a lot of PM.  Back in the mid-1960's, that might have been OK, but, meeting the NRSC emissions mask today may be a real problem (if used as the main in the broadcast band).  If it is a back-up, that's another issue.  I wonder why someone would bother retuning it when there are other transmitters available - any of the quad of 4-400-based 1kW boxes would be much better, and easier, to retune and use.  When I retuned ours in 1990, I used an old AM Stereo exciter (type accepted, so OK to use for broadcast) and drove the box.  That was easy.  (Don't try to do stereo, though....that transmitter makes so much Incidental PM that it can't be done unless the entire transmitter exciter is replaced with a good 50W transmitter with all the drive power swamped in the grid network termination.)  The only retuning was the drive output coil and the PA Pi-L network.  We would get about a year out of tube; then it was time to rebuild.  When we saw the cost projections to keep it going, we quickly bought a Nautel SS box.  My power bill literally dropped by 80% from just under $400/mo to $80/mo and that included the tower lights! (Mind you, this was in 1991). 

I currently use mine with an external 50W driver; it takes about 18 watts to make 375w carrier with network and swamping losses.  I don't use any feedback, but, at that power level, I am well under 3% distortion from 50Hz through 6kHz.  It is interesting to note that the original exciter would do well unedr 1% distortion when carefully tuned (and with feedback in use) but it still splattered pretty bad due to all the incidental PM taking place.  We saw about 20 degrees of PM (about 0.35 radians or so) at 95% AM....that's a lot!

They make killer ham rigs, though.  Build a matching network (L or Pi-net) and drive it directly into the PA, no feedback, and you get a kW of carrier and 125% positiv modulation (that just over 5kW PEP - did it once...into the dummy load).  The box is capable of 145% positive peak into 50 ohms at 1kW carrier.  Just not very clean, spectrally speaking when the internal exciter drawer is used.  Plus, if the exciter is clean, there is no overshoot, etc to deal with audio-wise.  It is a killer linear amplifier! 

One last thing:  Add snubbers, and varistors, across the primary of the plate transformer.   We used to blow up the expensive HV diode modules quite often.  I finally built a board that uses a stack of 1kV PIV, 3A diodes in series stacks, fullwave bridge configuration.  You can use the K2AY diodes, but make sure that you have transient protection.  Not many 1kW rigs have a 5400VDC supply - the only other one I know of was the Collins / Continental Baby Power Rock series PDM rig (with a -8500VDC supply). 

I have a full manual somewhere; should you be missing any information, email me and i can send you what you need.

73,

greg - k9qi

[flintstone mop]

The Vanguard TX was supposed to be as close to hi-fi a station could get for audio. Not a fun transmitter to maintain, obviously.

[K5UJ]

I always thought it would make a good AM amp if someone wanted to go that route but I never knew the specifications.  After reading Greg's specs I guess I could maybe tolerate the motel ice machine cabinet.

But broadcast is a different story.  I love tubes and have zero interest in solid state for ham radio but if I were running a station as a business, I'd invest in one of the 250 or 500 w. s.s. rigs for backup unless I was broke.  Some of the lower powered AM rigs cost about as much as a fancy ham plastic radio now.

Rob

[flintstone mop]

VERY inefficient for power usage, and it did not look like a Bcast transmitter. Like you say Rob, an ice machine or a juke box.

Fred

[Mike/W8BAC]

Come on now, say something nice! As an amp they really do a great job. If you look for a Vanguard, you want the 1 and not the later model 2. The 2 was built in an 8 foot ugly cabinet with NO personality at all.

I think of an old slot machine. Wish I had photoshop skills.

[DMOD]

The Vanguard diode low level modulation scheme was interesting.

As long as the RF to Audio voltage ratio was 3:1, you could get great audio out of it. Audio feedback from the RF final detector ciircuit was set to about 8 dB on average.

The exciter contained two crystal circuits of course and each crystal oscillator had a two transistor circuit, one for oscillation and one for buffering. Unfortunately, I do not have the pinouts, only the basic circuit. The RF from the osc./buf circuit then went to an RC amplifier which bumped up the RF voltage level to feed the diode modulator (below). The RF from the diode modulator then fed a 3 transistor SS (bi-polar) linear amplifier.

The output of the SS linear drove the grid of the single linear amplifier stage, which had about a 13 dB power gain, as I recall.

Phil - AC0OB