RS T-15 CC Coupler

that is the chief cook and bottlewasher of the other popular part 15 site selling that coupler. it's a good deal if you trust the seller enough to grab it. i did not check his feedback rating to see what it was as i haven't the cash for coupler. i'm trying to sell gear myself to fix what is not working around the station here. in addition to my computer issues i now have lost the main output transistor in my BV3001W certifed fm transmitter and am off the air on FM.

with that said

if i had the cash i would jump on all that C-C stuff regardless of who is selling it or how i regard the seller as long as their feedback rating was good.

I am in the audience waiting for the "Challenge" taking place at the other forum, in which certified AM transmitters will compete like a sporting event to see which one comes out on top.

It's kind of like picking "teacher of the year" when all the teachers are good.

I've got season tickets.

So - did the rules change here where you aren't allowed to mention hobbybroadcaster.net ? I only mention it because it seems like all of a sudden one day, everyone started saying "the other site" (I swear I hear DUH-DUH-DUNNNNN in the background) - its not voldermort you know...

it's to avoid any legal/lawsuit troubles with the other sites owner either personally or the forum here. the individual has acquired what shall we say an inflated ego and has gotten too big for their britches and has developed a large God complex. it's not out of the realm of possibility that the individual would sue either the forum masters or us users personally if we defame their little kingdom over there. a chance i personally do not want to take so we don't mention the name of any other site or their owner here.

All things considered (hope NPR doesn't sue) I personally am in favor of ALL Part 15 activity, all the forums, all the products, all the station owner operators...

But I don't necessarilly mention other sites by name as a courtesy to THIS site, so it doesn't appear that I'm trying to switch traffic in another direction.

He has been talking up his transmitter challenge for a long time without making much progress other than collecting a bunch of free transmitters.

He's the one responsible for the three slick videos here: http://www.iamradio.net/instructions.php. Now, tell me, which transmitter in his "challenge" collection do you think will get the highest rating?

He has a history of supporting and feeding other posters in his small circle who enjoy trying to discredit certain manufacturers with unsubstantiated allegations.

certain individuals participating in this forum check your inboxes/spam/junk folders for a private reply from me regarding phils statement above. very long read and took me an hour to compose it. it brings up some very intersting observations if you can read through the whole thing.

According to what I think I know the FCC requires that Potomac FIMs be calibrated every two years to remain acceptable to federal standards, and the typical cost of a factory re-cal is $1,500 plus.

The challenge may be held up while this detail is tended.

Today I removed the circuit card from the CP-15 Carrier Current Coupler I bought "as is", and find its general appearance to be clean and in good condition.

But the circuit board underneath R1 & R2 is browned from heat, so I took a look at a photo on eBay of another CP-15 Coupler for sale, and clearly saw browning on that card also.

R1 & R2 are 10 Watt 25-ohm resistors and provide a load to the transmitter during setup.

The CC transmitters provide a 50-ohm output to the input of the CP-15 Coupler, and when set to "Match," the signal passes to a toroid transformer T1 and then to R1 & R2 which are wired in parallel. I was surprised by this, since putting two 25-ohm resistors in parallel puts the impedance at 12.5-ohms! I would have expected the resistors to be wired in series for a load of 50-ohms, but no, I double checked the schematic and sure enough, they are in parallel.

The Theory of Operation regarding the Coupler reads: "The MATCH position of S1 activates the bridge circuitry and, through transformer T1 lowers the bridge driving impedance, dummy loads 90% of the RF input power for protection during setup."

After checking the 10 Watt resistors to be sure of their health, the Coupler will be connected for a real-world test.

Woot! Can't wait to hear how this goes.

Carl,

Since you have the CP-15 on the bench, would you please provide me with a few details? Although I have already bought parts to build one (still waiting on those Russian rotary switches), it would be helpful to have some accurate measurements. All I had to go on was a photo, from which I estimated a few things.

First, would you please measure the inside diameter, outside diameter and thichness of each toroid? Second, the toroid used for the SWR circuit is sideways, so I can't be sure of the number of turns. It looks to me that there are either five or six turns of each color wire (every time a wire passes through the toroid, it counts as a turn).

I have calculated several tap positions on T2, which is the 5-tap toroid. I have two strong possibilities for winding my own T2. Of the two, I'm leaning toward 7, 9, 11, 13, 15. It would be helpful if you could tell me the exact tap points.

Now, as to your confusion about the dummy load resistors. The two 25 Ohm resistors in parallel is correct. The first toroid has a 2:1 turns ratio. This gives a 4:1 impedance ratio. 50 Ohms divided by 4 is 12.5 Ohms, which is the value of the two parallel resistors.

Also, as to the claim of dropping 90% of the transmitter power in these resistors, I calculated about 86%, but I may be off somewhere in my calculations.

Joe

This may be of great help.

If you visit the Radio Systems website you can search for the Manuals for their carrier current equipment, including the current CC transmitter, which includes a detailed description of the parts and the schematics of the CP-15 Coupler.

I think ALL the information is given, including the toroid form details, number of turns, all the parts, etc.

Spend some time going over all that, and if something is still unanswered, come back.

I have the manual with schematic. Although most of the parts are listed with actual values, details on the toroid transformers is vague. The toroid transformers have an in-house number, as do a few other parts. Some information regarding windings is on the schematic, but not the number of turns or tap points.

No information about the size or type of ferrite core is listed. I have made a guess on the ferrite type by calculation, based on my estimated size of the toroids. BTW, from the picture, it looks like the toroid used in the meter circuit is smaller. Your measurements will confirm or refute this.

Although you won't be able to determine the ferrite type, the dimensions would help. I know that there is wire on the toroids, however, eyeballing the toroid while measuring should let you get a close enough measurement of the bare toroid itself. If you can get to at least a 1/16th, that will be fine. Toroids come in certain sizes, so I can pick the closest size to what you measure.

I have gleaned all the information I can from the documentation that I downloaded. If you have a document that has more detail, I'd love to see it.

Joe

Mojoe!

I carefully measured the three toroids NOT including the thickness of the wire windings.

T1 = 3/4# X 1/4"

T2 = 1" X 3/8"

T3 = 1" X 3/8"

Something to start with.