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Yep..mistuning the amp is just that...mistuning the amp..may reduce power output but the vswr stays the same. My guess is that the amplifier is producing a strong 3rd harmonic but at the same time the fact that he said that one antenna system shows a better vswr than another tends me to...

That is correct. You can run it with only 3 at reduced power in and out. Or if the tubes are pretty much new order up one and throw it in. They won't be exactly matched but they will work just fine. Back in the day when the 811-A tube was very popular they didn't match the tubes they just made...

Did you check to see if it already has the TDAs? Some did some didn't. Also check the VCOs and make sure everything is locking. Sometimes if you are lucky a simple alignment can bring it back to life.

You can..with some circuit changes depending on the device you want to use. Can you justdrop in different transistors...no. You need to match the input and output impedances of the circuit to match the devices and also make sure the idle current is correct. Also..while on subject...why? It is a...

Yes, if you're using it inside of a vehicle, you almost HAVE TO use an outside antenna. You are talking and trying to transmit inside of a big metal shield. Use a small mag mount. If you are using it outside the antenna that it comes with will work but realize a mile in a dense area is really...

Yep, that is what I was saying in my first post. But I think he said he tried it with different radios, etc.

I usually change the coax to RG-8x and have gone up to about 1500 watts without any issues. Haven't done more than that through a mag. I was never fond of the rg-58 they use and also the connector/adapter.

Hello everyone. I had an idea..might seem silly but I was wondering, since 10M has been open lately and a lot of the guys on here have 10 meter capability either because they came from 11 meters and it was easy to get on 10 after getting their ticket or the fact that they had 10M to begin with...

My guess is common mode. Do the choke right at the base of the antenna and ground the structure it is mounted on.

All I can say is wow! I worked on a few of these throughout the years and almost forgot what a deathtrap they are. The HV section looks like I remember although the one I was working on had 4 total 4cx250b tubes in it. Very poor design but at least there was a chassis there. The lack of grommets...

Go with the loop. Feed it with the 450 ohm ladder line. If you must you CAN use the halfway decent 300 ohm twin lead..just get the halfway decent foam type they have it at RadioShack. It will actually work believe it or not.

If I was there..I would take my kenwood HT (has hf rx) and tune it to receive on the frequency it is happening on. Then have you transmit first having the ht near the equipment. Then see if we can pick up the noise after unkeying and listening on the ht. If we can then keep duplicating it moving...

It has got to be something logical...maybe some parasitic or oscillation from something nearby picking up the TX RF and causing the circuit to become unstable in some nearby device then it settles down? Just throwing ideas out there. If anyone figures it out I am all ears.

Welcome to the hobby. Don't worry right away about the cobra antennas. You will have a lot of fun with the 980 and when you see fit..upgrade the antenna. I would do that before anything else. Have fun and if you ever have any questions there are a lot of good people here that I am sure would...

Mercury switches? We need to get Riggs and Rog on this..providing they aren't too old for this "sh@t"

300ma? Something is wrong. Mistuned, bad component, or excessive drive.

I have seen it before where the PA section (output section) or the amp afterwards has some type of oscillation but barely...and it fizzles out after a few seconds. But not convinced this is what you're dealing with. Heck..I've seen it in a few receivers as well.

BTW..Tony..how does that gizmotchi beam work for ya?

I just gave a cq call on the above mentioned frequency and nothing. Turned to 11 meters and it has been dead most of the day as well.

Back then they were cheap, plentiful, and also a trusted Motorola part. I was never a fan of the mrf455 too much gain but the 454 I had used in many projects and homebrew designs. The 2290 is a stout transistor though and has some great charachteristics. When ran properly the IMD performance is...