How to hook my driver

[tulmkr]

Hello again folks. I now have a nice little driver amp for Heathkit I picked up yesterday. My new question is...How do I hook up the 80 watt driver to drive the Heathkit? Do I just run a jumper from the driver output to the Heathkit input?

Please forgive my ignorance, but I really dont want to blow the thing up.

[drdx]

What model heathkit is it? It sounds like you have the coax part right but that heathkit will probably need to be "keyed". A typical cb amp is RF actuated, meaning the signal going in triggers the amp's relay. The heathkit probably has a key jack on the back. You'll need to rig up either a foot switch to key it or use a radio that has a provision for keying an amplifier. Or, I've seen the amp itself modified to be RF actuated.

If it is a heathkit sb-220 you won't want to run it over a few hundred watts deadkey (carrier) and just let the wattage swing up from there. They're good for about 1300 watts output. They say 2kw on them but that's the input power inside the amp, not the output. If it is the SB-200 you're good for 600w or so out.


-drdx

[tulmkr]

Yes its a sb-200. I talked to a guy who runs one locally and he is going to set it up for me in about a week. Since I have a few other amps to play with I was thinking of using one of those in the meantime. Since my driver amp is actuated by the radio rf, wouldnt the rf from the driver key the bigger amp? I honestly dont know enough to say one way or another, im just looking to learn what I can, and cant do, and why. Thanks for the reply.

[Nagant]

No it won't actuate the SB-200 as DR.Dx mentioned. You will need an external keyer to complete the circuit. With a CB setup I use push button momentary switches to key my Heathkit or Ameritron. A flip switch will work as well or a foot pedal switch as he mentioned. You will have to interface your key device via an RCA male plug to the back of the amp where the female key jack is. On a simple two position on/off switch you just need to take the center conductor of the cable to one lug of the switch and outer shield to the other.

[tulmkr]

So would it be the same for my contex 500, or the maco 300? I also have a palomar 300a that I was going to put in line, and use my eci as a driver. I can adjust the deadkey of the eci anywhere from a 5-50 watt deadkey. Can I just run a jumper from the eci out to the input of any of my other amps without needing a keying switch?

[Nagant]

You are talking about completely different amps. The Heathkit is a amateur radio amp and that is why it's 100 watts drive and uses a key circuit interface meant for a Ham HF radio. The other amps you mentioned were built for CB radio and therefore have their own internal key circuits. So no they don't key in the same method.

I wouldn't be putting any amp in front of the Palomar 300a unless your careful enough to make sure to set the control on the back for direct drive, however they labeled it. That takes the two drive tubes out of line to allow direct higher input to excite the four finals. If you forget and drive it with the drive tubes enabled be prepared for possible sparks and fire as it won't appreciate it. The tubes in that amp are expensive and harder to come by now.

That Palomar 300a is an exception as very few CB had that feature to disable the drive tubes

Don't put that little E.C.I. amp in front of the Contex of Maco if you want them to last. Those amps were made for lower power standard CB radios and nothing more.

[tulmkr]

Thanks for the input. The only reason I wanted to drive the contex, or maco a bit harder is because the radio I use most of the time is a sonar fs-23. It only deadkeys 3, and swings to about 20. I wanted to hit the maco, or contex with about 9 or 10, and let it swing. 3 watts out of the sonar would be ok for a small solid state, but my old tubers take a bit of time to start swinging, and seem to have a hard time getting to 500 watts.

[Nagant]

Here is a link to the manual for the Palomar 300a. [Please login or register to view this link]

I looked at a few pics of those amps online and it appears not all of them had the feature to disable the drive tubes on the back. It might have been more prevalent of a feature on the Palomar 350Z amps but i thought I have seen some 300a's with the same feature in the past.

[tulmkr]

Based on what the manual says, I can drive the palomar safely with about 40 watts from my eci, and it should, in a perfect world put out about 235 watt deadkey, and swing to wherever it wants to go. If that is the case, then I can just run a jumper from the eci into the palomar (on low). Set the eci for a low deadkey, and bring it up slow until im getting full power from the palomar. Does this sound about right?

[drdx]

One thing to keep in mind is that going easy on an amp and getting a few hundred watts is going to give you about the same signal as cramming a bunch of drive into it. It takes 4 times the power to raise your signal one s-unit (or "pound") on a meter. So, if the amp does 300 watts it would need to be raised to 1200 for one pound increase, so mashing it to 500 out isn't going to do anything for you, and you may as well let it loaf along and last longer.

Would you rather be putting an 8 on a friends meter 15 miles away on a given amp for 10 years or a 9 for 3 weeks? It really just depends on your operating style.

The more power you have, the worse it gets. If you're doing 600 on that heathkit, it will take you 2400 to see a difference. That's when it makes more sense to start dumping your money into better antennas. That's where the real bang is, and that's where the receive picks up too.


-drdx

[Nagant]

Well you seemed determined to drive them. It will be a learning experience for you as those sweep tube amps won't take what you want to give them. The Heathkit will as it's a whole different type of amp built for higher drive.

I wouldn't tune or run any of the CB amps like the old manuals from the manufacture state as they generally wanted to sell you some new tubes as well. Those tubes were so common and cheap back then but not anymore. As stated those Maco, Contex.... amps were meant for low drive radios like your Sonar and not to be driven with another amp. But they are yours to do with as you please. Have fun with it as that's what the hobby is about but it teaches some hard lessons sometimes as well.

[tulmkr]

Yea, I see what ya mean about the 4:1 requirement. The biggest problem where I am is that I am stuck in the middle of a big city, and get hammered from all directions. I cant put up a beam to turn 3 directions off, and the imaxx just sucks everyone in. Co-phasing the imaxx antennas would just make it worse. I mainly talk to a buddy who is about 20 miles out, and he has the power to get over the more local folks, so I am in need of about 800 to blast my way through. I have done all I can with audio, I run a full studio rack, and can modulate like mad, but I need the carrier to get it to where I need it to go. I guess I will just wait a few weeks until the Heathkit is set up properly, and just sell off the other amps, or hold them as standby's. I quickly put the palomar in line, and ran the eci into it. I heard some noises I didnt like so shut it all down. Not worth blowing up a decent box for some short term talk.

Thanks again for the replies, I really appreciate it.

[drdx]

Interesting. If I had one friend I regularly talked to and in your situation I'd cook up a wire beam or one of aluminum, fixed, in his direction that I could switch to. Or.........both of you go flat. The difference in horizontal to flat signals is about 20db. You could both run cheapo $5 dipoles if the others are all in mobiles or vertical bases and cut right through them on the same channel. Or........just use a different frequency, your choice. If you want privacy, use cell phones. If you love radio and want it, go to a different frequency. If you love radio and to drive them crazy, go to the flat side. If you like to tangle with them do the fixed beam deal, use a vertical one, or get really mean and talk split back and forth with both of you a couple of kc's above and below them and you're fine.

Proximity is huge too. It doesn't matter what you have if your friend has people in close proximity to him blocking your signal. A punk 2 blocks away barefoot from him will kill your best efforts.

-drdx

[tulmkr]

Yep thats exactly right. We both grew up together, and recently got back into the hobby just to see what we could do with what we had on the shelves. Of course it spiraled a bit, and then it just became something that had to be done. In a couple of months we may put it all abck in the attics, and be done with it. It was a great winter hobby, and now its just become a mission. Maybe one week when the wife is in vegas I will put a up a little beam, and try to convince her it was always there. Until them we just keep adding watts. Bored middle aged guys with too much time on their hands.

[drdx]

Well, don't let it be more than a hobby, it is just for fun, and don't let irritating locals drive you off the air. I think that's a huge factor in why the hobby has shrunk so much- irritating operators that make it just not worth it. There are other ways to drive them crazy, like dropping a few transmitters on their channel under their antennas resulting in a huge multi-deadkeyed tone generating pain on an otherwise busy radio night, but that's just a temporary fix. Maybe I'm assuming that you have a local jerk factor and maybe you don't. There are always other channels but I understand the quest/mission part. But, if the locals are jerks and you and your friend do end up putting it all back in the attic, and I hope you don't, then they win, for now. Then, they become the eventual losers as they're the last lonely operators out there, all alone, looking pathetic, with no one to talk to, much less harass.

In the equipment department, whatever you do, dont' become the guy with 20 radios and 20 amps that is out ther making noise but not dominating. Sell all of that stuff and get one big awesome setup that makes a statement. What good is 10 base amps if they all only do 750 watts? You can't add them all up. Get serious about it and get something with meaning, in the 2kw or more range, with a good antenna, nice and high, and forget that old coax. Get something like LMR400 or some new RG213 of a reputable brand so half of your signal isn't lost in cheap coax. If you're running the same coax you have shelved for years then that may be some of your problem. Have fun, hang around, and make it happen.

-drdx