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Messages - gil

#2596
After building a K2, I long for some simplicity... And what could be simpler than a vintage 50s tube transmitter? The Ameco AC-1 is a cheap one-tube (plus one rectifier tube) Novice transmitter that was sold as a kit for around $20. These days, they have become rather sought after, and go for more than $300 on Ebay! I found mine for $50, but as you can see on the photo below, there is much work to be done. Someone had the bright idea of drilling a hole for a key plug right through the Ameco logo on the front! I guess back then, nobody expected these transmitters to become collectibles...
There are also two extra holes in the back and there is an SO-239 plug added, which is not original. The antenna plug, I will keep. The key jack hole in the front has to go. So, my step by step plan is:


  • Remove all components and hardware.
  • Weld-fill the hole in the front and two holes in the back.
  • Sand and paint the transformer
  • Sandblast the chassis.
  • Have the chassis nickel plated.
  • Have the chassis powder coated on the outside.
  • Silk-screen the front panel with original print.
  • Mount all the components back in.
  • Call CQ on 7030!

Suggestions and questions are welcome. Stay tuned for more...

Gil.
#2597
Antennas / Re: A magnetic loop antenna for 40/30/20m.
January 07, 2013, 01:57:50 AM
I experimented with a 330pf high voltage capacitor in parallel with the air variable. I can tune the loop on 80m with a 1.1:1 SWR! Good news, but it is very inefficient. Though, Ray heard me, barely, 800 miles away. With 12W in, I am sure the amount radiated is measured in milliWatts... Reception isn't that great either, but hey, it works.

The loop will be painted in the next few days, bright red!

Gil.
#2598
Antennas / A Ladder Line Slim Jim for 6m.
January 07, 2013, 01:48:45 AM
Ah, I forgot to post this one... Completed before my 6m magnetic loop. It is a simple ladder line Slim Jim made of 450 Ohm ladder line (http://thewireman.com #551), solid copper. I wish now I had chosen the multi-strand 16AWG type (#552) because the #551 is very brittle and breaks easily. Not a problem since I mounted the antenna inside a PVC tube, but it would break soon or later if I rolled it up often for portable operations. So, the next one will be more flexible..

The idea came from: http://www.astromag.co.uk/j-pole/
It's really a Slim Jim, not a J-Pole.
Total length of the ladder line is exactly 14ft.
The quarter-wave length side is 54-3/4"
Gap is 3.15" (easier to measure 80mm).
It is fed 5.6" (14.2cm) from the bottom.

The ladder line wires are soldered together at the top and the bottom.
(If you bend the copper 90deg, it will break, solder a piece of wire between the two..).
The 80mm gap is cut without removing the plastic. I slice it, cut the copper and pull the piece out.

Here is how the antenna is fed:


Here with the Palomar Engineers RF choke kit:
(They don't seems to sell the kit anymore, but they have the ferrite beads: http://palomar-engineers.com)


The PVC tube is 10'+4' joined by a coupler and epoxied.

Here is how I attached the ladder line to the top end-cap:


SWR is 1.6:1 on 50.4, and 1.5:1 below that. I get the same SWR on my 2m copper tube Slim Jim... I haven't heard anyone on the air yet, so I can't give an on-air report. I am sure it works just fine. I will definitely make a "roll-up" model for 6m, and another for 2m, to be used with an HT. I have a 25' RG-174 patch cable that I will cut in two to feed them both. Those two antennas will be great with my KX3, and fit in a small pouch. You can make one in 20 minutes without breaking a sweat...

Gil.
#2599
Watch the videos...: http://www.team-blacksheep.com

Gil.
#2600
Antennas / A Magnetic Loop for 6m.
January 03, 2013, 02:50:49 AM
Hello,

Since my big loop works so well, I decided to build one for 6m. I have a couple working Gonsets (Communicator III & G-50) which are mostly used on 50.4MHz. I haven't heard anyone yet, but i am hoping a 90% efficiency loop will help. Great thing is, it is only 1.4ft. in diameter!

Be warned that magnetic loops are dangerous! Lethal voltages are present on the exposed parts while transmitting, and 6m is the worst wavelength as far as RF exposure goes. DO NOT stay near the loop while transmitting, and DO NOT let anyone get near it!

I started with a 3/8" soft copper coil. It came in a 25' long coil, and I have enough left for two 10ft. perimeter loops (more on that later). The length of the copper is 56 inches. My capacitor is a 3-37pf air variable (Hammarlund) available here: http://www.surplussales.com/Variables/AirVariables/AirVar1.html. The support tube is a PVC 1" thick-wall type. I also got an end cap and a "T" coupler. The screws used to secure the cut ends of the copper in the PVC tube are 1/4" brass. The toroid used for coupling is an FT-140-43.

First step was to calculate a maximum efficiency loop on 50.4MHz without getting to low on the capacitor. The program used is RJELOOP1.exe:



7pf is too low. It turns out that RJELOOP1 overestimates the capacitor value a bit. The same thing happened with my 20/30/40m loop, which ended up being a 30/40m loop due to my 9-110pf capacitor being too high, or the loop being slightly too long. I made the same mistake here with the 6m loop. 4ft. would have been better. But back to the construction:

Here is the top cap and tube drilled using a drill press and 5/8 drill bit:



Below is the bottom where the loop will be fed, thus creating a horizontal polarization:



I had to open up another rectangle window below the round holes to allow for the wire to go through the toroid a few times. Here is the result:



The capacitor is bolted on the PVC tube, through the end cap and the tube. A few washers on the bottom keep it level. I made slightly larger holes on the other side to get a screwdriver through.. I was not very happy about not being able to test the conductivity of the brass screws to copper tube connection (impossible to solder inside the PVC), so I used an external copper wire, which I soldered to the copper tube, then to the brass screws and the capacitor terminals.



Here is the completed loop with a 12" ruler for size:



I still need to put an SO-259 plug on the T coupler. Right now I used a binding post. At first I was able to thread five turns of wire through the toroid. As soon as I plugged it in, I new it worked! Though the capacitor plates barely overlap for peak band noise, which means my loop is a tad too long. It is fine, because the highest frequency it will be used on is 50.4MHz AM or below on SSB. SWR looked like 2.5:1, which is of course too high. I used a smaller feeding wire and managed to thread 7 turns through (every time the wire goes through the toroid counts as a turn..). The SWR got down to 2.1:1. I need to experiment some more. The SWR should go down to at least 1.5:1. My big loop gets 1.3:1... Maybe adding a couple turns will do the trick..

The loop is of course not meant to be carried by hand, though some people do that. I think it's crazy and way too dangerous. Look at the top image, it says 2750V with 27W in! I plug in another piece of PVC tubing into the T to get it high off the ground and away from anyone's reach or head... At first I thought I would paint it, but I like the copper color and might just spray a coat of clear acrylic on it..

Here is the latest addition to my stables, and the reason for building the 6m magnetic loop:



Now if only someone would answer my calls!

Ya'll have a happy new year!

Gil.
#2601
Antennas / Re: A magnetic loop antenna for 40/30/20m.
December 25, 2012, 08:21:22 PM
This one:

http://www.ebay.com/itm/E-F-Johnson-split-air-variable-capacitor-large-2-section-part-number-152-504-3-/251202802177?pt=LH_DefaultDomain_0&hash=item3a7cda9201

For air variable capacitors, since they are only one turn, I wouldn't use one with a range of more than 100 or 150pF. Otherwise, tuning will be difficult. Mine is a 9-110pF and is hard to tune already. the slightest movement of the knob throws the SWR way off. Also get one that has at least a 2KV rating, and that probably limits you to 10W (to be calculated), prefer a 4KV model. If you go too low, it will arc as you increase power.
Look at the link I posted previously, Surplus Sales of Omaha, if I recall.. They have good ones, though a bit expensive. Snatch that one above, it's a good one.. You can also put in in parallel for more capacitance or use the two gangs separately.. Gives you more options..

Gil.
#2602
Antennas / Re: White Tiger's Antenna Raising (part deux)
December 24, 2012, 05:23:04 PM
And maybe we can try again, see if the change made any difference..
NVIS 40m...

Gil.
#2603
General Discussion / Merry Christmas to everyone!
December 24, 2012, 12:29:52 PM
Hello,

It has been a few months since the site opened, and we already have more than two thousand posts! Thank you everyone for your contributions. I am wishing a merry Christmas to you all and your families. Because of your hobby, values, outlook on life, preparedness and self-sufficiency, I consider you guys my friends. I hope you all have a great year and that 2013 does not bring us events that would require our skills.

Gil.
#2604
No, nothing on this site was "rolled back" (I know, I own it). Maybe on another thread somewhere, but I don't recall seeing it. Well, newer radios have more features, and might receive a little better, but on the air, there is little difference. When you listen to someone's transmission and there is no drift, you can't know if the rig used is from 1950 or 2012... They are heavy for sure, due to the weight of the transformer and hefty construction. The Gonset has a steel chassis for each module, power supply, transmitter and receiver. They can be swapped from the radio independently. Great design. They sure look cool.

The only downsides are the weight and the high voltages that can still be present in capacitors after you unplug it. I always unplug the radio while it is on if I want to open it up. This way, the capacitors drain. Though that is not a guarantee.. It is good to use a grounding stick and touch all capacitors with it before using your fingers! Also recommended is to start with your left hand in your pocket and use your right hand only.. I hate being shocked so I always take extra precautions.. I certainly wouldn't put my hands in there with the power on!

I can understand someone calling it a paperweight. Probably teasing  ;D In a way, they are, but it's a cool paperweight that does transmit and receive just fine for less than $100. By the pound, it's pretty cheap  ::)

Gil.
#2605
Quotelol, what happened to the guy's post callin the radio a paperwieght or whatever, he mightve been a backstupid mudduck, lol.  but its also a mudduck move to delete the opinion.

There has been no answer to this thread but yours, so I do not know what or who you are referring to... Could it be on another site?

Gil.
#2606
I love old stuff and restoring old stuff. Not just because it is old, but because it is often better built and simpler. How often do you hear "They don't make them like that anymore.." To some extent, it is true. Not only that, but today, you usually can't fix it yourself. I wouldn't dream of diving into a recent model car or trying to fix a surface-mount components radio. We don't fix things anymore, we throw away. That's probably good for the economy in a way, but wasteful. It also assumes that replacements are available... We don't assume that replacements will always be available, do we? Otherwise this site would be called "radiofriends.com" or something like that. So, we often find ourselves evaluating old technology that we can understand and fix with a hammer and a pair of pliers.. Well, sort of.. Although I am only 45, I still remember tube televisions. My Grandmother had one. When the TV started misbehaving, she would open up the back, wiggle the tubes until she found a bad one and replace it. I don't know how she survived all those incursions into high-voltage cold-war era electronics, but the TV worked, and we didn't have to call the serviceman or buy a new one.

The first Ham radio I ever bought, before going nuts building kits, is a Gonset Communicator III 6m AM transceiver built between 1957 and 1961:



First, you have to admit, it is a bundle of cuteness. More importantly though, it is built like a tank. Proof is, it still works! After about 55 years... These radios were built for Civil Defense purposes and intended to survive a nuclear attack from the Soviet Union. There are no chips inside, no transistors. Nothing to fry from an EMP. The schematics are rather simple and any run-of-the-mill electrician could probably fix it, especially if he is in his 70s! I just ordered a second one actually, and might still get more to restore or as part sets. They sell for about $60 to $100 and more for restored units. There is also a 2m model, which I hope to get as well. Best thing is, you only need a Tech. license to operate one.

These old radios need some TLC mind you. All electrolytic capacitors need to be replaced, as well as, probably, most or all resistors. A restored set is pretty much ready to go for another half century, assuming you have a set of spare tubes. They are not very susceptible to high SWR. The Gonset will also work on 115V or 12V. It isn't a mobile unit by any means, nor is it intended for long distance communications. The 6m band has it's moments though, and the miracle band earns it's name once in a while. For local communications, with 6W, it works great. Besides, who is going to listen to you on 50.4MHz AM? Right... Nobody! I've been turning it on every night and never head a soul. I wish they still made them, but I probably would not be able to afford one, because they would cost a fortune. I hope some Chinese manufacturer reads this and gets an idea.. Many third world countries could use something like that. Think about it, when you open a modern transceiver case, you're supposed to wear an anti-static bracelet and put it on an anti-static mat.. What does that tell you? The Gonset, short of being hit directly by lightning or thrown off a boat in salt water while turned on, will survive anything.

Are they still a viable option today? I think so. I wouldn't use them as my only option of course. What you get is a semi-portable radio insensitive to EMP, on a seldom used (and listened to) frequency, with a range of maybe ten miles, more with a beam antenna.. For $100, and even for $300 restored, it isn't a bad deal. You also get to bring back to life a piece of the past, and that is priceless.. I will post my restoration progress on this thread, so check back often.
#2607
Antennas / Re: A magnetic loop antenna for 40/30/20m.
December 22, 2012, 04:09:54 PM
The big loop works so well, I have decided to build two more! One for 15/17/20m (10' perimeter) and one for 6/10/11m (4.5' perimeter). They will be made of soft copper tubing and thus have a nice round shape. Feeding will be through FT-140-43 toroids, though FT-140-31 would be better.. For the medium loop, I want to use the same capacitor as my big loop, 9-110pf. For the small loop, ideally, 5-70pf or something like that.. I will post the calculations later. I plan on using PVC water pipes for the handle/frame. The feeding will be at the top and capacitor at the bottom. This way the loops can be hand-held and the capacitor turned with the thumb. At the top I will have a 90deg elbow with maybe 6" of tubing ended by a BNC plug to extend the feeding line away from the loop. Not sure if that's the best way to go, and I might feed at the bottom.. More on that later.. The small loop will probably be fed at the bottom and made to plug directly into my Gonset Communicator case...

These two antennas will be cheaper than the big loop. No elbows to buy, little soldering, and for the small loop, a smaller capacitor. I just ordered the toroids..

I am also looking for a 300pf 2500V capacitor to use in parallel with the air capacitor on my big loop and tune 80m. Performance will be low, but at least it will work!

Gil.
#2608
Thanks Recon Prepper, very informative!

Gil.
#2609
Best wishes to you Anthony...
I still might move to your island some day  :)

Gil.
#2610
General Discussion / Tube Radios For Prepping?
December 18, 2012, 05:24:18 PM
What are you guys thoughts about tube rigs for prepping?

I have a Gonset Communicator III 6m AM transceiver, and this thing is built like a tank. Still works just fine even though it was built in the 50s. I don't think it would be damaged by an EMP. It doesn't mind a high SWR too much either.. Of course it is a base only option. Within a group or family, for local communications, it would work just fine. More private then CB. There is nobody on the lower portion of 6m in AM! I am not worried about leaving out 24/7. Most of my other radios (tiny CW QRP rigs) live in a metal box when not in use. You only need a tech. license to use it..

And what can I say, it is fun and warms up the room nicely in the winter! (photo of the radio on the Nets forum).

Gil.