Globe King 500 Mods

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K1MVP:
Quote from: David, K3TUE on October 05, 2005, 07:10:42 PM

Quote from: K1GXT on October 04, 2005, 01:51:18 PM

Just wondering if anyone has really dug into a Globe King seriously.  I've read everything I can find, including the AM Press Exchange and ER, and there's not much out there on performance improvements.


Quote from: Jim, W5JO on October 04, 2005, 03:08:11 PM

I guess one could do all you outline, but if you are going to do that, why not homebrew a complete set and sell the GK for cash.


I was just reading some things about the Globe King 500 on the net.  This transmitter (as well as others in the Globe lone) strikes me as not only powerful and rugged, but also seems relatively simple and easy to understand in design.  Despite all of this, should I assume it is not a good one to start off with?  Or is Jim's comment about homebrewing one as good advice as any for a first Plate Modulated transmitter.

Maybe I'm just thinking too big.

Opinions welcome.


Hi Dave,
Being a "conservative",--I believe in starting at a "lower level" and working up
to the "higher level", so I would not consider building a 500 watt transmitter
a good "first project".
I would think building a 75 to 100 watt plate modulated transmitter a much
better "first" rig to learn and get the "feel" of what is involved,--and you also
can have a lot of fun with a lowered powered transmitter on the air.
Just a few of my thoughts,--and it will be a lot easier to find parts for
a lower powered rig.
                                          73 , Rene, K1MVP     

David, K3TUE:
Quote from: K1MVP on October 05, 2005, 10:30:20 PM

Being a "conservative",-- [...]
I would not consider building a 500 watt transmitter a good "first project".
I would think building a 75 to 100 watt plate modulated transmitter a much
better "first" rig to learn and get the "feel" of what is involved,--and you also
can have a lot of fun with a lowered powered transmitter on the air.


I suspect 75-100W is good enough for 40, but is it enough to be heard on 75?

Quote from: K1MVP on October 05, 2005, 10:30:20 PM

[...] it will be a lot easier to find parts for a lower powered rig.


No doubt.

W1LSB:
In his recent post, David, K3TUE said:
"This transmitter (as well as others in the Globe lone) strikes me as not only powerful and rugged, but also seems relatively simple and easy to understand in design.  Despite all of this, should I assume it is not a good one to start off with?  Or is Jim's comment about homebrewing one as good advice as any for a first Plate Modulated transmitter.

Maybe I'm just thinking too big."

Well David, it's big, but not complicated.  The Globe King is about as simple as it gets from a circuit point of view.  True to form, all WRL transmitters suffer from short cuts in the power supply and tank circuit areas, and this rig is no exception.  I've spent most of my career in RF systems for TV broadcast, so I tend to be over cricital when it comes to good design practice.  Truth is, Leo and his Globe rigs put a lot of people on the air at reasonble prices.  I can't really fault him for the short cuts; some of them were pretty ingenious, and, he had to stay in business.  My real goal here is to figure out how make it play better (in my own warped mind) using minimal invasive surgery and modern components.  I'm still benchmarking the original box, then I'll start.

The RF deck can be thought of as a Globe Scout with a one more stage of amplification; the 4-250.  Globe added time sequenced keying, which is a really nice touch for CW lovers.   The modulator is nothing special, but includes its own plate supply, which is a real plus even if the B+ is a bit wimpy.  In later models, the PS deck includes a 755 VFO, which is pretty doggone stable if the components are OK.  Having three separate chassis does make it a challenge physically, but electrically, it's no worse than a Valiant.  If you've ever torn into a DX-100, Valiant, B&W 5100, a 32V, or any of the standard AM rigs, you're ready for a Globe King or Globe Champ, in my opinion.

Home brew is an excellent way to learn, but finding time and parts can be a challenge.  The 100W level on 75M can be pretty good, that what a 32V puts out, and they seem to do OK. The key is fully modulating the carrier.  On 40M, I've had pretty good luck with my Globe Scout 680.
The 350W level is the next logical step.
Your mileage may vary. 

73, George - K1GXT

K1MVP:
Quote from: David, K3TUE on October 05, 2005, 11:08:28 PM

Quote from: K1MVP on October 05, 2005, 10:30:20 PM

Being a "conservative",-- [...]
I would not consider building a 500 watt transmitter a good "first project".
I would think building a 75 to 100 watt plate modulated transmitter a much
better "first" rig to learn and get the "feel" of what is involved,--and you also
can have a lot of fun with a lowered powered transmitter on the air.


I suspect 75-100W is good enough for 40, but is it enough to be heard on 75?

Quote from: K1MVP on October 05, 2005, 10:30:20 PM

[...] it will be a lot easier to find parts for a lower powered rig.


No doubt.



Hi Dave,
When I mentioned starting out on a "smaller level",--I assumed you meant
you wanted to homebrew a "first" rig.
If you are familiar with commercial rigs in general and used lower powered
transmitters,--I would agree that the transition to a Globe King would not
be that big a deal(case in point)--I had a GK back in the mid 60`s and
did not find it hard to use the rig after having numerous lower powered
rigs,(i.e.--a Ranger, a Viking 2, a DX-100, etc)

BUT when it comes to building a rig from "scratch",AND getting it to
work properly, with a "clean output" with no harmonics and spurious
emissions,--proper neutralization, etc, etc, then I think its a lot easier
to build a "low or moderate powered" rig to learn the "basics", as far
as layout, wiring techniques, oscillator--final amp, interaction etc, etc,
not to mention the problems that can arise in a "high powered" PA
with improper impedance matching, and neutralization.--cause when
things go wrong in a high powered rig,--they can  go wrong fast.

As far as getting on with 75 to 100 watts on 75,--Most Dx-100`s and
Viking II`s run about 100 watts out and you will hear lots of em on,--
You may not be a "big strapper", but who cares?--you will be heard
and still have a lot of enjoyment, AND in the process you will be on the
air and talking getting ideas from other guys who have built the "bigger"
rigs.--Just a few of my thoughts,

                                   73, Rene, K1MVP

P.S., I was on yesterday on 75 am with my FT-101,(barefoot) at about
       25 to 30 watts out and had a great QSO with guys in Maine and
       Conn,--and was Q5,--may not have pegged thier S meter, but so
       what?--still had a great QSO.
       I still think a homebrew pair of 6146`s would be a great HB xmtr. 
 

KL7OF:
It looks like the HV power supply is choke input..(swinging choke?)  if you put a low Value (1/2 to 3 mfd) oil cap between the xfmr output and the choke it will increase the HV output of the supply.......simple and effective if the HV xfmr has the current capacity....I too like the looks of the GK 500..

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