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This is the procedure to convert a R-390 IF deck to work in a R-390A as was done in the R-725. Tom, N5OFF, wrote this in 2000 I believe.

The main difference between a R-725 and the R-390A is that the R-725 utilizes a custom built IF deck that is very similar in construction to the R-390 IF deck. It has tuned circuit selectivity instead of mechanical filters. The mechanical filters of the R-390A created distortion when that radio was employed for radio direction finding use.

In an internal Collins engineering report published in 1952, Lou Couillard wrote of the improved R-390A, which at that time was called the R-390(XC-3), "Although the superior shape factor of the mechanical filter IF is desirable in most applications, consideration should also be given to an alternate tuned circuit design for use in special applications. The excellent shape factor of the mechanical filters precludes the possibility of linear phase shift across the passband. Where a linear phase characteristic is desired such as in direction finding equipment, a tuned circuit IF is necessary."

Employment of the tuned circuit IF is exactly what was done in the R-725.

Motorola was awarded a contract in 1956 (476-PH-56-91) to prototype the R-725. I know of a couple of these Motorola sets existing today. Packaging of modified sets for quantity DF use were handled by Arvin Industries and Servo Corporation of America.

Approximately three hundred R-390A's were modified to the R-725 configuration. These sets are relatively tough to find today. New IF decks were manufactured by the modification companies (actually salvaging some of the components from the now junker R-390A IF decks) and installed in existing R-390A's. The new IF decks were named "SERIES 500 IF STRIP ASSY." They looked almost just like R-390 IF decks (see the comparison photos), except that the IF connectors were relocated to match the cables and connectors in the R-390A chassis. The circuits were designed to plug and play in the R-390A instead of the R-390. The decks are not interchangeable (until now that is, after performing the modification described herein).

Notwithstanding DF capabilities, a side benefit of the SERIES 500 deck is that it provides a smoother sound than does the stock R-390A IF deck. Mechanical filters are said to "ring" and after a while can be fatiguing to the listener. The purpose of this article shall be to describe how one may "roll his own" SERIES 500 IF deck from a surplus R-390 IF deck. Please note that I don't advocate trashing of a good R-390 to do this mod. The IF deck I started with came from a Motorola junker.

I would urge you to likewise find a junker R-390 as a source of an IF deck for this project . Make sure that the deck is in working condition prior to beginning the modification.

The R-390 IF deck was designed to operate with one 25V filament supply. The R-390A deck was designed to operate with a combination of 6.3V and 25V filament supplies. The task involved in this conversion is to rewire the R-390 filaments to conform to the voltages available in the R-390A and provided at the main IF deck connector, plug and play, without the addition of any new power transformers. Each of the twelve tubes in the R-390 IF deck must be addressed for full compliance with the voltages available from the R-390A.

Plug P112 of the R-390A shall be plugged-in to the R-390 IF deck at jack J517. There is much commonality here, except for the connections mentioned herein.

In general, you will be converting 25V series connections into 6.3V (herein referred to as 6V) parallel connections for most tubes, and moving the connections of the BFO/PTO/ballast tube series to a different connection point in jack J517. The 6V filament supply shall be provided to the R-390 deck by pin 20 of P112 from the R-390A.

General instructions: Refer to the schematic for the original R-390 as the "before" schematic. Use the best soldering technique you can in this limited access space. Don't insulate or bind any wires until instructed to do so. You will be utilizing some of the new 6V supply connections more than once. Make sure you can recognize your new wires. I used black wire for the 25V supply, red wire for the 6V supplies, and green wire for new grounds.

The first task is to install a B+ dropping resistor to better match the 180V B+ that the R-390 IF deck is expecting. To do this, locate inductor L503 under the IF deck. This will be found snapped into a holder right above pin 2 of J517. Disconnect one end of the coil, and install in series with it (the equivalent of) a 470 ohm 2 watt resistor. This will tame the B+.

The first tube circuit we'll work on is the ballast tube circuit.

V508 (5749) and RT512 (3TF7) These must be supplied by the R-390A 25V filament supply. To do this, sever the connecting wire at pin 8 of jack J517 (underneath the deck) to free this slot up (hint: save access to the connector end of the wire as you will use it to wire supply to V509). Then, sever the connection at pin 2 of RT512 and wire this pin to pin 8 of J517 of the R-390 deck with a long piece of new wire. The filament return connection remains unmodified. This modification will make the BFO/PTO/ballast tube series connections identical to the R-390A 25V filament supply connections. As mentioned above, this 25V supply is insufficient to supply the remainder of the tube filaments, thus the need to employ the 6V supply for this task.

The following 6V tubes shall have filaments wired from the 6V R-390A supply. The filament pins of these tubes are pins 3 and 4. Don't sever any connections unless instructed to do so. The modification will use as much existing R-390 IF deck wiring as possible (and thus may seem a bit screwy to you until finished).

V504 (6BJ6) 6V will come from its existing connection at pin 4. Ground will come in the next step.

V503 (6BJ6) Wire pin 3 of V503 to pin 4 of V504 for 6V supply. Ground V503, pin 4.

V502 (6BJ6) 6V supply will come from an existing connection at V503, pin 3. Ground V502, pin 3.

V501 (6BJ6) Sever ground connection at V501, pin 3 and wire pin 3 to V502, pin 4.

V505 (6AK6) 6V supply will come from existing connection at pin 4. Ground will come in the next step.

V506 (6AK6) Ground pin 4 of V506. Wire pin 3 of V506 to pin 4 of V505 for 6V supply.

V509 (6BJ6) Locate the free wire which was cut from underneath J517, pin 8, and connect it to the 6V filament supply at J517, pin 20.

The following tubes are 12AU7's wired in various series schemes in the R-390. They must be rewired according to their 6V option for use in the R-390A. Note two of the connections require dropping resistors on the 6V source of V507 and V510 to obtain the desired 5.3V filament voltage.

V511 Sever ground connection at pin 5. Connect pins 4 and 5 together for 6V supply, ground pin 9.

V507 Sever connections at pins 4, 5 and 9, including the two resistors (one 120 ohm and one 22 ohm). Wire 6V supply from your previous work at V505, through the deck opening for variable capacitor C525, to pins 4 and 5 through a 3.9 ohm, 1 watt resistor. Ground pin 9.

V 510 Sever connections at pins 5 and 9. Ground will come from existing pin 4 connection. Remove 120 ohm resistor between pins 4 and 9. Wire pin 5 to pin 4. Wire 6V supply from J517, pin 20 to V510 pin 9 through a 3.9 ohm, 1 watt resistor.

There are no changes to any of the other connections in the R-390 deck.

Prior to installing the modified R-390 deck in your R-390A, you must check your work.

Perform continuity checks from J517, pin 8, with RT512, pin 2.

Perform filament supply and ground continuity checks as follows. Note: There will be more than one ground connection at various tube sockets, but the filaments should have continuity exactly as shown.
Filament supply is checked from J517, pin 20.

V501, filament, pin 3; ground, pin 4.
V502, filament, pin 4; ground, pin 3.
V503, filament, pin 3; ground, pin 4.
V504, filament, pin 4; ground, pin 3.
V505, filament, pin 4; ground, pin 3.
V506, filament, pin 3; ground, pin 4.
V507, filament, pins 4 and 5; ground, pin 9.
V509, filament, pin 4; ground, pin 3.
V510, filament, pin 9; ground, pins 4 and 5.
V511, filament, pins 4 and 5; ground, pin 9.

Now insulate any bare connections, and use mini-tie wraps to secure the new wires to sturdy nearby points.

To enable final installation of the deck in your R-390A, you'll need to make two adapter cables. These cables shall consist of jumpers (RG-59 is OK, approximately eight inches in length) with BNC's on each end. You'll also need two adapters of the type found on the back of the frame of the R-390A at the IF OUT jack (AMPHENOL 47200). This will provide crossover from MB connection (R-390A standard)to BNC (R-390 standard). Connect P-218 of the R-390A to J-526 of the R-390 IF deck with one of the cables. Connect P-213 of the R-390A to J-525 of the R-390 IF deck with the other cable. It is a good idea to label these cables. See the photo for reference.

Install the deck in your R-390A. You will notice that the screw holes are the same as for the R-390A IF deck, however the screws of the R-390 deck are of larger diameter. I did not change these screw as they are captive into the deck. The BFO, BANDWIDTH, and power connector of the deck will hold it in place, however I would not install it in a Jeep this way. Changing these screws is optional.

When you turn on the power, make sure your dial lamps light up normally. If they don't, you have a filament supply problem so turn off the set immediately and troubleshoot.

For great sound, instead of using the built in audio deck, I prefer to tap the audio from the diode load jumper at the back of the set. Through a 0.1 uF or larger capacitor, feed this signal into your line audio amp of choice, and enjoy the tuned circuit audio of the new R-725, errrr, R-390A with tuned circuit IF. You'll get the smooth sound of the R-390 and R-725, but have the parts availability and support common to the R-390A for the balance of the set. I've used my modified IF deck in two different R-390A frames, and it worked equally well in both. In my opinion, it makes the long term listening experience much more enjoyable.

Tom Marcotte, N5OFF
A great accomplishment with many more to come...
Technical Stuff / Re: Collins R-390A Meters - Should They be Opened?
« Last post by W1RC on June 20, 2018, 10:58:17 AM »
Many R-390 and R-390A receivers were sold by the government with the two meters missing and the obvious question has persisted for years - What happened to the meters?

The answer is that the materials used to make the dials glow in the dark are radioactive and hazardous.   They had to be disposed of according to a specific protocol.

However before this policy was enacted many receivers were sold with the meters and another question that has persisted is how much risk there is if one *does* open a radioluminescent 390/390A meter.?

This is a very tough question.

The answer is interesting and was posted on the r-390 List by Charles Steinmetz <>

“My answer is:? I know nothing about you, or your abilities concerning careful detail work that requires fine dexterity and hand-eye coordination, or your ability and willingness to follow instructions
down to the last detail.? Therefore, I must recommend that you *DO NOT* open a radioluminescent 390/A meter *for any reason*.

If you decide to ignore this advice and *do* open such a meter, you must absolutely, positively insure that you are the only person who could possibly be exposed or endangered by your activities. I also recommend that you *study* (not just "review") the AEC/NRC cleanup protocols, as well as the standards and protocols that govern working with materials that contain Ra226.? You will also need to ensure that you have laboratory-grade radiation monitors ($$$) available at all times.

At a minimum, you will need an indoor space that is relatively well sealed (doesn't exchange air with the outside environment).? You will need to enter this space and seal it up, and have available at least one laboratory-grade radiation monitor (preferably two, for sanity checks)? You will also need to have a reliable communications device you can use to contact your local HAZMAT authority, as well as the contact information for that authority.

This means that no part of any dwelling occupied by others may be used (whether they are there at the time or not).? *Period*.? You at least need a standalone building (preferably small) located at least 50m from the nearest other building.

So, the drill is:? Seal yourself in and do your work, continuously checking the radiation monitors.? Clean up, putting all leftover radioactive materials into radiation-safe containers that are shielded
for the types of radiation emitted by the item(s) you were working on (alpha, beta, and gamma in the case of Ra226).? Check for residualradiation *everywhere* in the space you are working in, including your own person and clothing.? Check again.? Check a third time.

If everything tests clean, arrange to have your local HAZMAT authority pick up the waste container(s) (or transport it to them, if permitted in your jurisdiction -- but be sure to *CALL FIRST* to alert them that you will be coming).

Now, here is the hard part.? If there is any residual radiation, *STOP* before you spread it any further.? Call your HAZMAT authority, explain the situation to them, sit down calmly, do not move or stir the air, and wait patiently for the nice people in radiation suits to come and decontaminate you and your space.

Now, do you still want to open up your meter?? If so, (1) keep your eyes wide open, (2) take full responsibility for what you are doing, understanding that radioactive dust is easy to spread and virtually impossible to collect after it is spread, and (3) take all of the precautions described above.? I have done this in the past, but I would not do so today because my manual dexterity may no longer be up to the challenge due to aging.”
Mister Mike’s Hot Cars / Programming Additional Miata Keys and Remotes Yourself
« Last post by W1RC on May 29, 2018, 11:19:03 AM »
As you probably know, the Mazda Miata has a built in security system that utilizes a key with an embedded transponder chip that is read by the car's ECU when you start the car. The ECU is programmed to accept only certain transponder codes. If a key's transponder is not registered with the ECU it will not allow the car to be started.

This is a system that Ford has developed and has so far proven very effective at reducing auto theft, while there is nothing that will prevent a determined, prepared car thief from stealing a car system like this make it nearly impossible to start a car by hotwiring or breaking the ignition.

Mazda North American Operations seems to think that their customers are complete idiots and are incapable of wiping their own nose. They don't include instructions in the owners manual for programming additional keys yourself, instead they instruct you to go to your dealer to have new keys made & programmed. As some forum members have experienced some dealers have wanted over $100 to make & program new keys.

Luckily my other car is a Ford Crown Victoria with the same transponder key system.  Ford I guess has a slightly better opinion of their customers so they provide instructions for key programming in the owners manual (which I retained in PDF format). I decided to take the risk and attempt to use the Focus key programming instructions to program new keys for the Miata.

First I needed a compatible transponder key blank cut physically to match my car's ignition & door locks. My local locksmith doesn't carry the blanks (some will) so I had to go to the Mazda dealer. The guy at the parts desk warned me that they needed to be programmed but when I told him I was going to program it myself he was like "ok". 5 minutes and $23.38 later I had a new key physically cut to match my existing keys. I tested the key in the ignition and verified that while it would turn the ignition cylinder it would not engage the starter, it also unlocked & locked the drivers door so I know it's cut correctly.

Now to program the transponder, I have the Crown Vic manual page in hand, here is the basic how-to.

Items needed:
1. 2 pre-programmed transponder keys.
2. 1 new transponder key

The timing is critical to this procedure, please read through the entire procedure before attempting.
1. Insert one of the pre-programmed transponder keys and turn the ignition to "on", leave on for at least one second (I wait until the red key symbol in the instrument cluster extiinguishes), remove the key from the ignition.
2. Within 5 seconds insert the second pre-programmed key and turn the ignition to "on" for at least one second but no more than 5 seconds (use the key symbol for this as well) then remove the second key.
3. within 10 seconds insert the new key in the ignition and turn the ignition to "on", if you are successful the red key symbol will illuminate then extinguish after about a second.

If you are not successful the red key symbol will flash repeatedly to indicate that you have inserted an invalid key. Remove the key, wait a minute and try it again, it took me a few times to get it perfect and I had done it before.

To see the applicable pages from the Focus owners manual see this page

The new key cost me less than $25, the dealer even physically cut the new key for free.

I STRONGLY suggest that EVERYONE go out and get at least one spare key made & prorgammed for their Miata. If you lose one of your two original keys and don't have a spare you won't be able to make any new keys (as you need two programmed keys to program more) and will need to go to the dealer and have them re-program the ECU.

Programming a Spare Remote for Mazda Miata

Step 1: Open driver side door and leave open.

Step 2: Lock and Unlock the drivers door using the power door lock switch on the door

Step 3: Insert key into the ignition.

Step 4: Turn Key to ON position and return to Lock (off) position. Do this 3 times within 10 seconds. LEAVE key in the ignition in Lock (off) position.

Step 5: Close and open the drivers door 3 times. Leave door open after this step

Step 6: ECU should respond by locking and unlocking the doors once.

Step 7: Press any button on remote #1 twice. ECU responds by locking and unlocking the car doors.

Step 8: Additional remotes, repeat Step 7 for up to 3 remotes total.

Step 9: Remove the key from the ignition and the ECU will respond a final time with a series (about 4) of door locks and unlocks. You're done!
NEAR-Fest XXIII May 4th and 5th 2018 / Re: Ham Jam!
« Last post by DrOptigan on May 06, 2018, 04:55:30 PM »
*pokes his head out of the bunker*

Wow, what a jam! A bit odd compared to the other ones, but I think we made it work. Thanks to everyone who put up with my keyboard playing and singing. Maybe we'll do Freebird at the next one..........  :P
aka Dr. Optigan
Follow the Odyssey of the Mind team's progress as they compete in World competition in Ames, Iowa at

Video of the New England Tech Trek, NE(T)2

From FACEBOOK posted by Jenny Gore 5/05/2018:

“This weekend was beyond crazy. We took seven 4th and 5th grade girls to #nearfest and the NE(T)2 conference to raise money for their Odyssey of the Mind World Finals trip. 

They were invited to/given a table in the technology building and were also given permission to solicit donations (no one has ever been allowed to do that before). THEN they were told that whatever they raise, the organizers would match up to $500.

The ARRL thought it was awesome, interviewed them and will be doing an article showcasing their solution.

These girls were so sweet and patient with everyone! Even with the older “seasoned” crowd that would talk about things over their heads, they would smile and ask questions. They made everyone feel special.

At the end, they had raised $455. During the closing ceremony, the head organizer guy “Mr. Mike” (see below) brought them on stage, allowed them to talk about their “odyssey”, then told the crowd how NEAR-Fest was matching up to $500, but they were a bit short of that. He then said, “Who will help them reach $500? Even a dollar will get them closer.”

Everyone lined up to donate! Everyone!! People just kept coming and coming. Their donation jar got so full that they had to take the lid off. Then it got so full that they had to squish bills down. Lisa had to walk away because she was crying, it was so beautiful! I choked back most of my tears, and hid the escaped tears behind my sunglasses. In the end, they came away with $1,214 dollars!

I cannot thank the amateur radio community and tech community enough. You guys and gals are the best people!! Thank you so much!!!”
NEAR-Fest XXIII May 4th and 5th 2018 / Door Prizes
« Last post by W1RC on May 02, 2018, 08:35:42 AM »
We will be drawing for the following prizes this time.

First Grand Prize:  Elecraft KX2 with KXAT2 Antenna Tuner, MH3 Hand Mic, KXBT2 Battery Pack and KXBC2 Charger.  Value  $1100.75.  Please note: Winner must provide their SSN as a 1099-MISC will be issued.  You do not need to be present to win.

Second Grand Prize: Radioddity GD-77 dual band VHF/UHF digital (DMR) walkie talkie with programming software and cable valued at $99.00.  You do not need to be present to win.

Second Grand Prize: Certificate for one night’s stay at the Holiday Inn Express, Manchester NH and a Guest Pass to NEAR-Fest for two people and one vehicle.  Value $180.00

Be sure to fill in your ticket stub and drop in the prize drum located on the stage at the Relaxation Grove.  PLEASE WRITE OR PRINT LEGIBLY.  Include telephone number and email address.

Drawings will be held at the stage at the Relaxation Grove at the following times:

Friday: 12:00, 2:00 and 4:00  Second Grand Prize: Radioddity GD-77 dual band VHF/UHF digital (DMR) walkie talkie

Saturday 10:00, 12:00 and 2:00 First Grand Prize: Elecraft KX2

Door prizes include a 2018 ARRL Handbook, courtesy of Ham Radio Outlet, a $50 ARRL Gift Certificate and a $25 ARRL Gift Certificate, compliments of the ARRL, a Certificate for one night stay at the Holiday Inn Express, Manchester NH, (value $150) compliments of the hotel.  You need to be present to win one of these prizes.

Door prize winners will be able to choose the prize they have won from the “prize pool” so the earlier you claim your prize the better the choice will be.

Winning numbers of unclaimed prizes from earlier drawings will be announced at later drawings during the fest so please attend to see if you won an earlier prize.  All Door prizes not claimed by 2:00 PM Saturday will be forfeited and redrawn at a later time. 

More to come so please check back later.
Mister Mike's "Mishigoss" Board / A Short Treatise on Men’s Leather Jackets
« Last post by W1RC on April 30, 2018, 11:37:54 AM »
Leather Jackets:

Men’s leather jackets are very popular for many reasons one of which is that, if properly cared for, they will last a lifetime.  Also they are comfortable to wear and never go out of style.

Military leather flight jackets, such as the iconic US Army Air Corps A-2 jacket and A-2 styled jackets are very popular.  Here is an excellent Web site that provides comprehensive information on the A-2.

It is important to know about the different types of leather used in the manufacture of jackets.

Cowhide is the most common leather used to make jackets because it is durable, easy to care for, and resistant to water and dirt. Its tough qualities are especially prized by motorcycle riders and police officers. Cowhide is affordable and functional.

Lambskin is very soft, luxurious leather. Fashion designers prefer its naturally light weight and velvety touch. It finishes beautifully, has a soft hand, and drapes well. With a little extra care, lambskin is very wearable and is the ultimate luxury.

Horsehide is rugged enough for military wear. That's why the Army Air Corps used it for the famous WWII A-2. High grade horsehide is supple and comfortable, but still tough enough for a military jacket.

Goatskin is perfect jacket leather because it is durable as well as supple, soft to the touch, and very comfortable to wear. Of all leathers used for,garments goatskin resists abrasion the best.  Goatskin jackets last so long they are passed down from generation to generation. I've seen goatskin jackets that look even better after 50 years of wear than they did when new. Both the Navy and Air Force use goatskin for their G-1 and A-2 flight jackets.

Leather Terminology.

Chrome-tanned - Leather preserved with chromium compounds and other mineral agents to produce supple leather for garments, shoes and gloves.

Vegetable-tanned - Leather preserved with tannins from bark, seeds, and wood to produce strong and slightly stiff leather for luggage and belting.

Drum dyed - Leather dyed in a rotating drum until the dye completely penetrates the leather.

Aniline - Leather dyed with transparent aniline dyes to produce a beautiful transparent finish and suppleness. No pigment is used, but a light finish may be applied to color or protect the leather.

Semi-aniline - Aniline dyed leather topped with a very light coat of pigment and finish to even out the color and increase durability.

Pigmented - Leather coated with resin containing pigment. Pigment gives leather a uniform color and shade. Low-grade leather needs thick coats of pigment to cover up cuts and scars.

Thickness - Leather thickness is measured in millimeters or ounces per square foot. One-ounce equals about 1/64-inch or 0.40 millimeters thickness. Jacket leather is usually between two and four-ounces.

Top grain - Leather from which only the hair and under flesh have been removed.

Grade - Leather grades range from A to D depending on the type and amount of flaws. Grade A hides are clean with no flaws. Grade B has a few slight imperfections. Grade C has healed cuts. Grade D has unhealed cuts. The higher the grade, the less pigment needed to finish the leather and the more beautiful the finished jacket.

Shearling - Sheepskin with the wool attached. The wool can be straightened or left naturally curly.

Mouton - Shearling tanned and finished for fur.

Leather Tanning Steps

Raw skins are soaked in a vat of salt brine to temporarily preserve them.
Preserved skins are soaked for several days in a solution of lime and sodium sulfate to remove hair and fat.
Clean skins are treated in a bating vat with an enzyme and sulfate or chloride to remove the lime.
Hides are placed in a tanning drum with chromium compounds or vegetable tannin.
Tanned hides are placed in a fat liquoring drum with oils and greases to increase pliability.
Hides are dyed with chemical or vegetable dyes in a rotating drum.
Dyed hides are milled in a rotating drum to soften them.
Milled leather is rolled, stretched, and dried to make it strong and uniform.
Leather is finished with pigment, wax, oil or glaze.
Finished leather may also be buffed or polished.

Sources of A-2, G-1 and other fine leather jackets. 

Formerly known as Flight Suits Limited, Gibson & Barnes of San Diego makes a very nice line of leather jackets.  My favorite is the Skyliner Airline jacket made for American Airlines pilots.

These companies manufacture A-2s and variations from original patterns and are for those who,want an authentic jacket that is wearable.  They are quite pricey, over a thou.

Eastman Leather Company, Devon England

Buzz Rickson, England

The Real McCoy, Japan

This,company manufactures their jackets in Turkey amd are made-to-order.

Then there is always eBay.

Repair and Restoration services.

Even though the leather is very durable and rugged the knit cuffs, waistbands and zippers often need replacing.  These resources also offer new lining, leather restoration and repair.

NEAR-Fest XXIII May 4th and 5th 2018 / Re: Ham Jam!
« Last post by Whoz Your Daddy on April 28, 2018, 07:22:37 PM »
Ham Jam!
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