I sure this topic has been brought up before but I can't find any info on the subject.
My Daiwa MR-750 rotator indicator took a jump of about about 180 degrees the other day.
The rotator still works but the indicator is way off.
It's been a bit jumpy for several years but always indicated the correct direction. I think the cold weather finally took it's toll on it.
My guess is the plastic drive gear jumped a few teeth.
If I have to take this all apart I would like to replace the pot. I know parts have long been discontinued and unavailable for years but I'm wondering if any one knows of a replacment pot that will work properly in the unit.

TNX...... Joe WB2NGX

I just want the antenna to work on 6m so I can get into a couple local repeaters so gain isn't a big issue. 100 Mhz and above haven't been affected. What I have noticed is if I wrap the jumper around the original coil it changes the SWR a little. I have to put the jumper some where under the plastic coil sleeve so the only option was to wrap it around the existing coil, I'm only talking about 1 1/2 turns but it does change things. I could try looping the jumper vertically rather than wraping it and see if that has any less affect, or I can just unwind the original coil to the correct length and cut off the excess or just remove it completly and use my jumper. I guess I'll have to play around a bit more. I'll never use the vertical part for any other band other than 6 any way.

I've cured the problem. Bypassing the coil with a 6" jumper brought the SWR down to 1.1:1 at 52.6 Mhz without even having to trim the original length of the whip. I hope I didn't change the wave length or the gain of the antenna by doing so.

I have a discone antenna that was made by CTE or ALAN International, made in Italy. It's well built but I could never get it to become resonate on 6 meters. It's supposed to transmit from 25 Mhz to like 1200 Mhz. It tunes fine from 100 Mhz on up.
There are no shorts or bad connections. The whip is about 57" long with a small coil in the base. Is it too long or too short?
The antenna does start to become resonate at around 26 Mhz, over 30 Mhz the SWR starts a rapid climb off the charts till around 100 Mhz and becomes normal again all the way up. Is this thing flawed by design or is the whip length incorrect??
All these discones are the same in design and have the same freq. coverage both TX and RX.


TNX..... Joe WB2NGX

Yes some older refrigeration appliances made prior to 1979 may contain PCB's.

A while ago I bought an old Heath dummy load..... full of oil. My main concern was weather the oil in it contained PCB's. Being an  older item I couldn't be sure. Since there is no way to tell by color or oder I decided to research it furthur.
What I found was a couple simple tests that don't require any special equipment or chemicals and any one can do at home.

The first test is for PCB's in the oil, called a density test.
Put a few drops of the oil in question in a glass of water. If the oil floats or sperads out on the top of the water it's free of PCB's. If it sinks then the oil contains PCB's. Since PCB's are heavier than water they will sink. Mineral oil is lighter and will float. However if any are detected this test doesn't tell the concentration amount.

The second test is a chloring presence test. This test checks for chlorine in the oil to determine PCB presence.
This test is done by taking a piece of copper wire, dipping it into the oil and holding the wire over a flame such as a propane torch. Observe the color change of the flame. If the flame strarts to turn green or blue green then PCB's are present. If the flame remains orange none are present.

The oil in my dummy load passed both tests. I changed it anyway because it smelled funny.

I can remember back when car AC systems were leak tested with a propane flame on a special wand. If the flame turned green
you were close to the leak area. I would imagine since refrigerant oils back then contained PCB's the same type of test was used. Later replaced by putting dye in the system and checking with a UV lamp.

So if any one ever wanted to know what might be in that old dummy load you brought back from the ham fest now is you chance to satisfy your curiosity. Please post you findings.

Joe........ WB2NGX

That is exactly why I would like to buy a gallon from any place other than the local drug stores. Thanks for all the input.
I have no clue as to what the stuff is that I removed. Looking at it in a clear plastic milk jug it's golden in color. Mineral oils that I've seen aare clear or slightly yellow. When you get this stuff on your fingers the smell is hard to get rid of.

I recently found a mint Heat Kit cantenna dummy load. It was a bit wet on the top as most are from carrying them around with the oil splashing and seeping through the ceramic insulator. I cleaned it all up. Research tells me these weren't shipped with oil...... it was up to the buyer to obtain the oil. Now, my question is I'm wondering what type oil might be in this thing??? I doubt there is any way to tell by color or smell. The bottom of the can has a coating of some sediment or fine light sludge, maybe some seperation of the oil over the years. It looks clear with a slight yellow cast. I emptied it into a plastic milk carton and wiped the inside of the can clean. I'm wondering if I should put it back in or look for some transformer oil. I don't know if this original stuff contains any PCB's or not. It does'nt scare me but to be safe I would rather put some oil of a know type back in it.

TNX......

Well that is the way I see it too. But if there is a short in the brake swiitch and voltage is leaking to ground it could be causing the problem. I've really covered everything and am at a loss. The only thing left to do is to remove the rotor and see if the problem still persists.

No intermittent contact between any of the traps or elements. The antenna was completely gone through last fall all connections and traps were cleaned and penatrox was applied to all the joints. Also, the brake doesn't cause any movement in the antenna what so ever. Possible shorted brake solenoid is what I'm thinking.

I know it's been a while since I started this post, we finally got around to checking all the traps on the antenna. All the traps were installed where they should be. The SWR still remained the same, OK on 10 meters, off the charts on 15 and 20.
Resonate on 18 where it shouldn't be. Here is what happened next........ I decided to turn the antenna while watching the SWR on the analyzer to see if any directional change in the antenna due to twisting coax would change the SWR.
Unbelievably what I noticed was just as I hit the brake switch on the rotor controller the SWR jumped even higher. Every time I hit the brake switch the SWR would jump all over the place.
With repeated pressing of the rotor brake switch I was able to get the SWR back to normal on all bands.
Now.............. after all this messing around with the traps I now have found that the problem is some how related to the rotor brake, I would guess as short??, the brake is feeding voltage into the tower and or possible faking the SWR analyzer into a false reading. By repeated hits on the brake switch I'm able to get the SWR back to normal. But there is more........ If I bump the brake switch to where I get a high SWR reading I can turn off the rotor and even unplug the controller and the SWR still remains in the high state, I can't figure that out. I can turn the control box back on, bump the brake switch a few times and get the SWR back to normal. This has really got me stumped. This is an old CDE rotor.
Does anyone have any ideas as to what might be happening here??

TNX...... Joe

I recently rebuilt a couple FNB-4 battery packs that I have for my older FT-727R HT. The new batteries are 1600 mAh nickle metal. I have had people tell me that you can't use the drop in charger with these batteries as it was designed for the older Ni cads. Back about 10 years age I bought a replacment pack that had nickle metal batteries in it and I never had an issue charging them with the drop in charger, but those batteries at the time were 600 mAh. So is the issue here the larger capacity of the new batteries vs the charge rate or what???  I have also been told that you can use the charger but don't leave the pack in there for more than an hour as the charger won't know when they are fully charged and when to shut off. I would think being a larger capacity battery it would take even longer to charge. Are there any mods for this NC-15 that will allow safe charging of nickle metal batteries??

TNX....... WB2NGX

Interesting post about the wall thickness of the capacitor tubes. I know the length is correct but I never checked the wall dia. I can''t see where .009 would make any difference. Mine by the way has the blue capacitor caps. I bought this antenna in I think it was 1992, but I believe it was made before that. The easy fix for the element standoffs or spacers was to put a dab of silicone in front and in back of the plastic spreader on each of the three elements that pass through it. Mine have never moved.

My SWR readings are as follows:
28.00 - 29.00 1.1:1 - 1.2:1   29.1 jumps to 2.5:1 and 29.2:1 and up 3.1:1
21.00 - 21.30 1.1:1 - 1.2:1   21.35 jumps to 1.6:1 and up
14.00 - 14.30 1.1:1 - 1.2:!    14.350 jumps to 1.5:1

SWR does vary a little depending on the direction that I have the antenna pointed probably due to my wire antenns I have strung from the tower. My 160 inverted L is about 5 feet below the beam.  SWR varies when the boom iis in line with the top hat of the wire. Can't be too fussy.

Thanks...... got it. But I can't really do much with it. I guess the rotor has to be hooked up.
Being a DOS program I don't think there is really much to look at or play with.