Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - k7rmj

Pages: 1 2 3 [4] 5
46
Greetings Roberto,
What values of styroflex capacitors are you looking for?

73 DE K7RMJ  Frank

47
Open Chat / Re: Happy Christmas
« on: December 21, 2016, 04:43:11 PM »
Thank you Paul. Here is wishing you and yours plus all members of this web site the same Happy Christmas.

Frank  DE K7RMJ

48
Open Chat / Winter Solstice
« on: December 21, 2016, 12:33:50 PM »
Today, December 21, is the Winter Solstice for the year 2016. What this means is, today is the shortest day of the year in the northern hemisphere of the planet. The sun goes down earlier and rises later each day until the Winter Solstice.

On the Winter Solstice it is CRITICAL that we all go outside at 12 noon and perform the Rites of the Sun! Without doing this, the sun will keep going lower and lower and within 6 months it will completely disappear and leave us in a perpetual, cold and dark, winter! You need to do the following:

1 = Find a small, dead, fuzzy critter such as a mouse, rat, hamster, rabbit, squirrel, etc.
2 = Use a pair of pliers and grab the small critter by the tail with them.
3 = Swing the critter around your head 12 times while chanting, "The aliens are coming" over and over.

This one small act will save us from the dreaded winter months and cause the sun to start rising earlier and setting later each day, thus gradually warming everything up again.

I know this works because I read it on the internet.

Seasons Greetings. I hope you all have a very Merry Christmas and a Happy New Year.

73 DE K7RMJ  Frank

49
Amplifiers / Heathkit SB-200 Rebuilt and cleaned
« on: December 20, 2016, 10:56:48 PM »
I acquired an old Heathkit SB-200 Ham Radio Linear amp from a friend a couple of years ago. This posting is about the cleaning and maintenance required on an old amp like this. They were first offered in 1964 as a "kilowatt amplifier" and sold in kit form for $200. See the attached PDF flyer for the original advertisement from Heathkit.

The amp includes two 572B/T-160L tubes in parallel. They are mounted horizontally and cooled by a small fan under the tubes. Back when this amplifier was popular the FCC required ham operators to measure their power as "input to the final amplifier stage". Today it is a bit different. Today we rate the power of an amplifier as "output power in RF".

My amp looked very good when I bought it. It was in almost perfect condition with no dents or scratches on it anywhere. The paint is original and is very slightly faded but for as old as it is that is no problem. See the attached pictures.

When I got it, I couldn't resist opening her up and checking out the innards. A couple more attached pictures are below. Notice the DANGER sticker in bright RED. They are not kidding. This amp has over 2300 volts DC under the hood. That IS lethal if you get zapped. I do NOT recommend you go poking around inside an amplifier like this unless you have considerable training and understanding about how to handle this type of gear. It should be unplugged and the power supply capacitors should be fully discharged before you even open the lid.

All the capacitors in the power supply have replaced with new ones. The Harbach modifications for inrush current and soft-keying are installed.  You can see the little green circuit board for the soft keying modification in one of the pictures. This is needed to key the amplifier with one of the modern rigs that cannot handle the 120 Volt AC relay that was used in the original circuit for transmit/receive switching. It would fry the amplifier keying circuit in your new solid state rig.

The inrush current modification gives you much longer life for the tubes. It clamps down the current to the tubes when the amp is first turned on while the power supply voltage comes up to full reading. At least, that is how it was explained to me.

I added a drop of Singer Sewing machine oil to the fan bearings because it was overdue for maintenance. The wife was very understanding about letting me borrow her sewing machine oil. I put it right back where I found it when I was done.... before she got home from the grocery store. Just don't tell her I borrowed it LOL.

Anyway, that's what I've been up to. I love this old amp. She is a real workhorse and puts out a very clean signal on the air. She will do 750 Watts output on CW with 400 MA plate current and 1900 VDC plate voltage, and 1200 Watts output PEP on SSB. On sideband that is 12 DB of gain over my 100 watt transceiver. S-units are generally 6db gain from one S-unit to the next. So the amp gives me an additional 2 S-units for the receiving station I am in QSO with.

Just remember, regardless of how tempting it is, keep your fingers out of the large power amplifiers unless you have a LOT of experience with them. Get someone with experience to help you and show you around the insides of one instead. Your friends and family will be glad you did.

Regards and 73  de K7RMJ  Frank

50
Antennas and Towers / Re: 40 Meter Bobtail Curtain
« on: December 19, 2016, 04:37:48 PM »
Thank you for the kind comments, Buddy. I'll dig a few more out and post them over the holidays.

73  DE K7RMJ  Frank

51
Antennas and Towers / 40 Meter Bobtail Curtain
« on: December 18, 2016, 03:43:58 PM »
I used to write a monthly column for our Ham Radio Club in Missouri. The attached document is one of the articles I wrote a few years ago. Let me know if you like it or want to see more of them.

Regards,

Frank  DE K7RMJ

52
Antennas and Towers / Off Center Fed Dipole or OCFD
« on: December 18, 2016, 03:20:39 PM »
This antenna is often called a "Windom" antenna. However, that is not quite correct. The original Windom antenna was fed by a single wire rather than an open wire feed line or by coax feed line, both of which have two conductors.

The regular dipole, which most of us are familiar with, has two halves that are equal in length. They are both a quarter wave in length and total a half wave in overall length for the antenna. It is just two quarter wave lengths of wire or whatever kind of conductor you desire, and the feed line from your radio transmitter is connected to the center of the antenna with one conductor soldered to each half of the antenna.

With the off center fed dipole it is connected the same way as a conventional dipole except that the feed line connections are center. For an 80 meter antenna You should make one leg of the antenna 45 feet long and the other leg about 90 feet long for a total of 135 feet. This changes the impedance at the feed point from 72 ohms to about 200 ohms.

On my 80 meter OCFD I made a 4 to 1 balun and put it right at the feed point. Then connected my Coax to the balun and ran it into the radio shack. I thought I was done then but discovered that I had a lot of RF floating around in the shack. So I made a coax choke balun and installed it right outside the shack.

I made the choke balun by simply coiling about 20 feet of coax into a 12 inch coil. That removed virtually all the RF from inside the shack and did not change the tuning of the OCFD.

Now the big question. Why go through all that fuss when a simple regular dipole would work on 80 meters? It's because It also now works on 80, 40, 20 and 10 meters with a 2 to 1 or better SWR which the tuner in my rig can take care of. It doesn't cover ALL of 80 or 10 meters with that low SWR but it does cover a significant portion of both and on 40 and 20 meters it covers all of the band with 2.5 to 1 or less SWR. So far It has worked into several states including Hawaii and Alaska as well as about 30 foreign countries. For DX stations it works into South America and Europe the best but that's because those areas are broadside to the antenna.

Regards and 73  DE K7RMJ

53
Holy cow!  This guy is so smart it's scary. I thought I was a pretty good technician until I watched this video and now I am humbled. Wow, he has an outstanding lab.

Thanks for posting this Buddy.

73 FRANK  DE K7RMJ

54
Equipment Review / Re: Sprague T03 Tel-Ohmike
« on: December 15, 2016, 04:27:47 PM »
It may be a few weeks before I work on that Sprague TO3. Good old PayPal strikes again.

I moved from the St Louis area down here to Hot Springs Village, AR in January 2016. Right after the move I went through all my accounts at various web sites and updated my address, shipping info, credit cards, etc.

Well, guess what? PayPal got my address change and entered it into their data base but that didn't stop them from giving out my old shipping address when I ordered some parts over the weekend. When I contacted them I was told that they have my current address for shipping and billing and it matches the credit card I have attached to that PayPal account and they are correct. The web site shows my current address for shipping to be here in Arkansas.

So I showed them a shipping receipt I got back from Parts Express where they sent my parts order to the address given them by PayPal... it was the old address. So, now I am waiting for them to wade through all the administrivia to get their mistake resolved and it may take a while before the Parts Express company receives their shipment back from the old address.

Sorry for the long winded whine but I wanted to let everyone know that this can happen. The PayPal representative I spoke with over the phone this morning said somehow that address was pulled from a historical file from old purchases made last year. She went through and purged their system of all my old shipping records to clear it up... I hope. She was very nice about it and wanted to help.

Anyway, life is still good here in Arkansas. I love living here in the woods. It's like being on vacation all the time.

Regards and 73  de Frank  K7RMJ

55
Design, Project / Re: Chrystal Tester Build
« on: December 14, 2016, 11:37:48 AM »
Hi Buddy and thanks for the kind words and good tips.

I was originally going to use the foil side of that board but it wasn't flat enough due to the etched surface and the little islands did not stick very well. So I used the other side of the board to glue the islands to. I got a much better contact for the glue to stick to the board that way.

Yes, old CB radios or computer headers would be a great source for the crystal sockets. Unfortunately when I moved down here to Arkansas I lost a lot of the small parts during the move that included anything useful for the sockets. The good news is that it gives me a good reason to start collecting new parts LOL. I think for now I'll solder a pair of alligator clips top a piece of circuit board and use the alligator clips instead of a socket. That should work for immediate needs until I get the collection or parts built back up.

I still need to solder the DC and the output connections from the board to the panel mounted jacks inside the case and it will be ready for use.

73 and thanks again
Frank  de K7RMJ

56
New member welcome / Re: New member saying hello
« on: December 13, 2016, 10:26:15 PM »
Thanks for the kind words RJ and Jim M. I've been perusing the forum here for the past few weeks when time allows and I am really amazed at the knowledge base available here. A really good and friendly group. Thanks for letting me join yall.
73 Frank  DE K7RMJ

57
Design, Project / Re: Chrystal Tester Build
« on: December 13, 2016, 10:19:30 PM »
Thanks for the kind words RJ. It was a fun build although it sure took me a lot longer than I thought it should. I guess my age is catching up with me LOL. Any suggestions about what to use as a crystal socket? I'm tempted to just install a couple of alligator clips on the front panel but that would not be real elegant LOL.

73 Frank   de K7RMJ

58
Design, Project / Chrystal Tester Build
« on: December 13, 2016, 06:14:39 PM »
Buddy inspired me with his posting of the Chrystal Tester that Alan posted. So, I dove into it head first. Home brew equipment is not real easy. I think the hardest part is laying out the parts on the circuit board. I used an old board from years ago when I was first learning to etch my own boards. I don't recommend etching your own boards unless it is for a really special and easy project that you will need to duplicate many times over.

I used what some call the "Manhattan style" board construction. In one of the photos you will see the little island circles. They are cut out of scrap, single sided, circuit board material. You just figure out where you want them and glue them to a blank or like I used, the bare side of an old left over board. You can see them in the photos. I used very slow drying super-glue to glue them in place.

Figuring out where to place the islands is the hardest part. One tip to making it a little easier is to basically lay out the parts just like they are on the schematic diagram. Wherever you have multiple parts to attach at a common point is a good place to put an island. Be careful though, you can get an island with too many connections on it and that makes it difficult to solder them all in place without messing up the other connections on the same island.

Before you start gluing the islands on the board you should lightly sand the side of the board you are gluing them to. Just rough it up a little. This gives the glue a good surface to stick to.

You don't have to use the perfect round islands like I did. I just happened to have a bunch of them in my junque box that I picked up at a ham-fest some time ago. After you glue all the islands in place it helps to tin all the islands before you start soldering parts to them.

I mounted most of the resistors vertically so they would take up less space. The capacitors I used are all from the junque box and that is why the .02 caps were disc ceramic and the 470 pf are tantalum caps. They are all the right value but just different in size. I wasn't too worried about using NPO caps for this oscillator circuit because it is for testing crystals which are inherently stable.

At first I was going to install the board in an Altoids tin. But, even though it would fit okay, it was just too small to fit all the connectors and such that I want mounted on a front or back panel. So I am using a small clam-shell case. Another item from my junque box. The difference between Junque and Junk is that the items in the junque box are much more fancy. LOL.

Well, there you have it. I am really pleased with this little circuit and test box. It works on the bench. Now all I have to do is get out the drills and make holes for the power, and output connectors and the crystal socket. I'm not real happy with the connectors I have for the crystal socket. They are the small, probe type connectors. I think something with a little better holding power would be much better.

Let me know if you have any questions, suggestions or corrections.

73 Frank   de K7RMJ

59
New member welcome / Re: New member from Houston area
« on: December 13, 2016, 05:37:25 PM »
Hi Bob and welcome aboard. I am new here too and have found the gang on this forum to be very friendly and helpful. I'll bet your experience in digital equipment and systems will prove to be very valuable with the modern equipment, radios, audio systems, etc. Glad you found us.
Regards, Frank   de K7RMJ

60
New member welcome / Re: New member saying hello
« on: December 12, 2016, 11:48:07 AM »
In another posting Buddy mentioned he likes to hear details about new members backgrounds. So, here goes.
I was interested in tinkering with radios before I was a teen ager. My Grandpa, W6DWC got me hooked on Ham Radio during a summer visit to his place over in California. My neighbor K7CUZ taught me Morse code and helped me get my Novice license.

In 1966 I joined the US Army and was trained in Electronics repair at the Ft. Monmouth, NJ Army electronics school. I graduated from their as a "Fixed Station Receiver Repair" technician trained on R388, R390, R390A and other receivers. I was stationed in Germany near Karlsruhe with a transportable communications company. Working with that equipment was like being on permanent Ham Radio Field Day. We covered the entire HF radio spectrum from 2Mhz to 30 MHz and provided 32 channels of teletype plus 4 channels of voice. The transmitters were 10KW and 40KW output.

After the Army I hired on with AT&T Long Lines, the long distance company for AT&T working in the Phoenix, AZ central office. Eventually I climbed the corporate ladder over the next 23 years until after they busted up the Bell System. It was a great place to work until then. I learned about telephone systems and networks and about data communications systems and networks. During all this time with AT&T I was transferred from place to place every 2 or 3 years and eventually gave up on AT&T while living in Fresno, CA and went to work for Sierra On-Line as their System Support Manager. That job lasted for about 4 years.

After Sierra On Line moved to Seattle Washington I left them and opened my own Telecommunications Consulting business in San Antonio, TX.

I absolutely loved working for myself. It was a lot of hard work, 16 to 18 hours per day, 6 or 7 days a week but I loved it. Then in 2001 the bottom fell out of the Telecommunications industry and I went to work as a systems consultant for a company in Indiana for a couple of years, then as a Field Service Manager for Black Box Network Services, then finally wound up in St Louis working for the best company of my career, Edward Jones LLP. I was their Senior Network Consultant for all their voice telephone systems. There were over 12,000 telephone systems with 36,000 telephone lines scattered all over the US, Canada and the UK. It was a lot like running a small telephone company. They were an outstanding company to work for and they really cared for their employees.

Then in March, 2016 I finally gave up working for a living and retired to Hot Springs Village, AR. That's where I am now and loving it. It's like being on vacation permanently. The forest here is beautiful. We are surrounded by the Ouachita National Forest and their are 13 lakes within a half hour drive. 

Okay, that's enough about my boring past. I am in the process of building up my workshop with enough test equipment to repair my own ham radio equipment and even scratch build some gear. I'll post stuff about the equipment as I get it working.

Thanks for all you do, Buddy. You have an outstanding forum here that is full of good ideas and tech tips. Wow, I didn't mean to make this so long. Oh well, think I'll post it anyway.

73 Frank  de K7RMJ

Pages: 1 2 3 [4] 5