307 Amps 2X6 Base Amp Issue

[nomadradio]

A 'scope is your friend. Setups that sound killer on AM will sound like doo-doo on sideband. If the radio is already flattopping and slicing off your voice peaks the amp will never sound right. If someone set the radio's ALC for a desired wattmeter reading, that could explain the radio's problem. The low-drive test with the radio alone will either reveal a bias fault in the radio. Or not. Turning the mike gain down to 1 or 2 Watts peak should sound clean. If it doesn't, that's just one of several likely problems with this setup.

The built-in driver creates a severe upper limit on drive level. Even if the radio sounds as clean as the driven snow it will have to be turned down so the driver transistors don't push the six finals to their "flattopping" limit.

In my experience you may find that the highest power level that sounds acceptable is one third or one half the AM peak power.

Not a hard and fast rule, just a typical trend.

73

 

[AK321]

I honestly believe my power supply is the problem, it's the AC hum making my audio sound bad because when the previous owner had it, it sounded great on SSB. Ordered a new one, should be here by the weekend.

 

[9C1Driver]

Checked out his web site, very cool and looks like he does good work. I think his best bang for the buck would be a biased 4 pill base amp. Not a big fan of amps with a driver stage (1x4, 2x4, 2x6 and so on). With most of today’s radio’s being higher power a driver stage is not needed. Something like an old low powered Cobra 2000 or 148 works great on a 1x4 or 2x6 amplifier.
Anyway you have a pretty sweet amp there. Once you get it dialed in and don’t overdrive it should sound great.

 

[AK321]

Sending it back to Jim so he can check it out.

 

[Xracerx13]

Try that again on AM but this time don't flip up the SSB delay switch the one with the blue light. That is why your seeing 4.77w for a couple seconds in the video when you unkey.
As far as your deadkey power... the radio output might be set a little low for AM. Whats that at?
The main power on is the switch with the cover on it I'm thinking.

 

[Shadetree Mechanic]

Doesn't that peak hold keep the number up when you quit talking?

 

[AK321]

Try that again on AM but this time don't flip up the SSB delay switch the one with the blue light. That is why your seeing 4.77w for a couple seconds in the video when you unkey.
As far as your deadkey power... the radio output might be set a little low for AM. Whats that at?
The main power on is the switch with the cover on it I'm thinking.

The center on the switch is standby. Up is AM. Down is SSB. The radio is deadkeying 2W, 20W PEP.

Doesn't that peak hold keep the number up when you quit talking?

It does. But using the tune and average settings, it reads zero untiI start talking, then drops back down to zero again. So zero deadkey power when not modulating.

 

[Xracerx13]

The center on the switch is standby. Up is AM. Down is SSB.

You can verify that when you get a chance at opening it up and looking at that switch. If the green wire is soldered to the bottom connection on the switch then up is SSB.
2 watts deadkey might be OK on AM for a 1 pill driving 4 pills but this amp might need a touch more.

 

[AK321]

You can verify that when you get a chance at opening it up and looking at that switch. If the green wire is soldered to the bottom connection on the switch then up is SSB.
2 watts deadkey might be OK on AM for a 1 pill driving 4 pills but this amp might need a touch more.

The relays chatter on SSB with the switch up, when it's down, it doesn't. Putting 5W dead key swinging to 45-50 PEP, and the amp drive knob at max power, I get 110W deadkey. So it seems I have to put more drive from the radio, to see any dead key wattage and it should be showing more than 110W. Jim @ 307 Amps told me to turn off mic gain, and increase drive until I see 150W deadkey, so I'll try that tomorrow.

 

[AK321]

So 5W deadkey and 45W PEP will give me 150W deadkey. Seems like a lot of drive for a 2 pill driver section, but I know little about solid state amplifiers.

 

[loosecannon]

AK321, your statement is a bit confusing.

you stated the drive to the amp in PEP numbers which are peak modulated power, and then noted the deadkey coming out of the amp.

i think you had the deadkey on your radio set at 5 watts, and then tried 2 watts.
what is the deadkey set at on the radio that is giving you a 150 watt deadkey out of the amp?
LC

 

[AK321]

AK321, your statement is a bit confusing.

you stated the drive to the amp in PEP numbers which are peak modulated power, and then noted the deadkey coming out of the amp.

i think you had the deadkey on your radio set at 5 watts, and then tried 2 watts.
what is the deadkey set at on the radio that is giving you a 150 watt deadkey out of the amp?
LC

About 5W, 35W PEP with the amp drive all the way open, which results in 150W and about 1400 PEP out of the amp.

 

[loosecannon]

thanks for the reply.

I think your problem is with the radio, the power supply supplying the radio, or the power supply in the amp.

what power supply are you using for the radio?

has the radio had any mods done?

do you have a way to check the input SWR? (SWR meter in the radio would give you this, or put a meter in between radio and amp. amp on, AM mode, deadkey only).
What is that SWR?

you also stated in a previous post that you were monitoring your output on a galaxy radio.
is this radio in the same room with all your other equipment?

im wondering if you are getting "on-air" reports from others or just going by what you hear in that galaxy radio.
it's so close to your other gear, it's probably distorting the receive audio.

i still have a hard time believing that a two pill 2290 section needs a 5 watt deadkey in order to drive a set of 6 pills to a 150 watt deadkey.

hell my 4 pill will do a 100 watt deadkey with 3 watts put into it.

the amp looks nice, and well built. it is biased for SSB the same way many other amps are.

before you send the amp off, it would be a good idea to try to isolate the problem to the amp.

the way to do that is to strategically substitute other equipment in to the chain and see what changes.

also, the more detail you can provide about your setup, the better help you'll get here.
im talking about starting at the power cord and going all the way through to the antenna, listing everything in line, meters and all, and giving relevant numbers where you can.

this will help the techs here set up some experiments for you to do like the one i proposed early in this post.
LC

 

[AK321]

I'm using a home built HP 75A power supply, which has a distinct AC hum in my audio, so I bought another power suppy. I think that it is most definitely a problem with the radio or power supply. And yes, the Galaxy is on my bench with my other radios. I agree that it might not be ideal for monitoring, sitting so close.

The radio has crappy audio on SSB without the amp. Passing crappy sounding audio through the amp just makes it sound worse. As far as my setup, it's a Radioddity QT 60, aligned and audio tweaked a bit to produce cleaner audio than stock, done by Scott's CB in March. 4 foot jumper to the amplifier, 6 footer to the coupler of my LP 400. Then into 50 feet of LMR 400 and connected to a Tram 1498 antenna.

 

[snippits75]

i still have a hard time believing that a two pill 2290 section needs a 5 watt deadkey in order to drive a set of 6 pills to a 150 watt deadkey.

It's six 2879C's. The 150 watt transistors.

Friend of mine had a 2x6 Fatboy. Nothing but trouble with the two pill engaged. It had a switch to cut the two pill transistor section off. Ran great on the straight six.