Shadetree Mechanic
Delaware Base Station 808
If you are willing to do some work to it we can probably help you get it set up correctly.
-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
heathkit sb-220 sensitivity knob? tune?
- Thread starter 552fl
- Start date
Shadetree Mechanic
Delaware Base Station 808
I don't have one yet. I will probably put up a beam first. Nomad would be able to give you the ins and outs. From what I know, which isn't much the SWR between the radio and amp needs to be checked. On my Contex amp I had to replace the variable capacitor on the input side because it wasn't big enough to bring the SWR down. On my TS350HD I had to do the same thing. Also because your amp is able to select 10m operation, it is close but still might need a different coil on the output. Then the bias of the tubes will need to be changed in order to take the AM carrier. And I am sure some other things that I forgot. And then maybe some more things because I never got the whole scoop on the conversion. So after all this then what would you have? Well for one it would be cleaner than any 4 pill but it also depends on the radio you are running and what you are expecting. If you are running a stock Cobra 29, then it will still sound like a Cobra 29. If you are running a tube rig then a tube amp will let it shine. As far as what power can be expected, some people run these so hot that the solder melts out of the tube pins. How much power that is I am not sure. Maybe Nomad will come back and give us the scoop on one that is set up.
Chris
thanks,chris
for all the input im running a galaxy 2517 base-d104 mic two towers one starduster at 65 feet--4-element beam at 45feet..have two donkey stomperamps 2-pill and a 1-pill then my texas star dx500 a texas star hdv-350 in my mack dump truck...I bought the sb-220 thinking to have a little more ump than the 4-pill..but I DONT wont to damage it I[ll just sell it and get the 6-pill I was looking at......roger
for all the input im running a galaxy 2517 base-d104 mic two towers one starduster at 65 feet--4-element beam at 45feet..have two donkey stomperamps 2-pill and a 1-pill then my texas star dx500 a texas star hdv-350 in my mack dump truck...I bought the sb-220 thinking to have a little more ump than the 4-pill..but I DONT wont to damage it I[ll just sell it and get the 6-pill I was looking at......roger
I,ll just key 40 watts rms into it and use it as a 900 to 950 watt box really like the look of the sb-220 looks good in the radio room..keep the dead key coming out of amp around 200 and let it swing to around 9 to 950pep use it like a baby box..
552fl,
That sounds reasonable. I believe that is what Nomad was trying to communicate early on.
I thought about your BBI comment and realized that if you ever watch his video's closely, you never see the average output from an SB220 long enough to make sense of the output. My bet is the average is less than 300 watts. It is the "Peak" reading bumping 2k watts that gets him business!
Treat the SB220 right and it will last a long time and give good (i.e. clean, not distorted) consistent output. The better your input SWR (to the Amp) is the cleaner output and less stressful it is on your driver set-up (2517, or 2 pill or??)
73's
David
That sounds reasonable. I believe that is what Nomad was trying to communicate early on.
I thought about your BBI comment and realized that if you ever watch his video's closely, you never see the average output from an SB220 long enough to make sense of the output. My bet is the average is less than 300 watts. It is the "Peak" reading bumping 2k watts that gets him business!
Treat the SB220 right and it will last a long time and give good (i.e. clean, not distorted) consistent output. The better your input SWR (to the Amp) is the cleaner output and less stressful it is on your driver set-up (2517, or 2 pill or??)
73's
David
One modification that reduces the heat stress in "SSB" mode is to replace the factory-original 5.6-Volt zener diode with a series string of thirty (30) 3-Amp rectifier diodes. Each one provides about 2/3 of a Volt of bias. Thirty of them in series adds up to about 20 Volts. This reduces the zero-drive tube current so that the tubes only push about 30 Watts of heat apiece with no drive. This leaves some margin for running AM in SSB mode without melting the tubes.
It's no big trick to build from perfboard. We make a DIY version, but there's more to it than just this alone.
Reducing the tubes' idle current will now change the input impedance of the tubes. The SWR on the amplifier's input when it's keyed will rise if you install this trick by itself.
We install this input-matching circuit directly under the tube sockets for a customer who wants an 11-meter only AM hot rod.
To make room, we move the fat blocking cap from where it was over to the input pole of the relay. Makes sense to also replace the coax feeding from the relay to the tubes' cathodes with teflon coax if you have it on hand. The capacitor on the input-side of the coil is 68pf at 2500 Volts. The output-side cap on the coil is 47pf at 3kv. A lower voltage rating would be vulnerable to breakdown if you get the tubes too hot and one of them arcs inside. The coil is 7 turns on 1/2-inch diameter, spread for lowest input SWR.
Beefing up the parasitic chokes is also a big deal. The harmonic current in the tubes will be higher running hot-rod AM, and overheat the stock parasitic chokes. We use three 100-ohm 5-Watt resistors in place of the original single 47-ohm 2-Watt carbon resistor.
There are additional measures to take that beef up other weak links in the chain for hot-rodding the SB220. Bypassing the band selector's output side works best if you tap the output coil one turn farther down from the original 10-meter tap point. This compensates for the stray inductance of all those wires on the band selector. Using the original 10-meter tap point may increase the Q factor of the output circuit in a way that makes the tubes run hotter than necessary.
But that's enough for today.
This is one of those "You just gotta want to" modifications. Trying to justify the cost by how much higher you'll drive up anyone's S-meter is not so easy, either. This sort of setup makes the SB220 safe to run 2000-Watt AM peaks or more.
Doesn't make it a good idea.
73
It's no big trick to build from perfboard. We make a DIY version, but there's more to it than just this alone.
Reducing the tubes' idle current will now change the input impedance of the tubes. The SWR on the amplifier's input when it's keyed will rise if you install this trick by itself.
We install this input-matching circuit directly under the tube sockets for a customer who wants an 11-meter only AM hot rod.
To make room, we move the fat blocking cap from where it was over to the input pole of the relay. Makes sense to also replace the coax feeding from the relay to the tubes' cathodes with teflon coax if you have it on hand. The capacitor on the input-side of the coil is 68pf at 2500 Volts. The output-side cap on the coil is 47pf at 3kv. A lower voltage rating would be vulnerable to breakdown if you get the tubes too hot and one of them arcs inside. The coil is 7 turns on 1/2-inch diameter, spread for lowest input SWR.
Beefing up the parasitic chokes is also a big deal. The harmonic current in the tubes will be higher running hot-rod AM, and overheat the stock parasitic chokes. We use three 100-ohm 5-Watt resistors in place of the original single 47-ohm 2-Watt carbon resistor.
There are additional measures to take that beef up other weak links in the chain for hot-rodding the SB220. Bypassing the band selector's output side works best if you tap the output coil one turn farther down from the original 10-meter tap point. This compensates for the stray inductance of all those wires on the band selector. Using the original 10-meter tap point may increase the Q factor of the output circuit in a way that makes the tubes run hotter than necessary.
But that's enough for today.
This is one of those "You just gotta want to" modifications. Trying to justify the cost by how much higher you'll drive up anyone's S-meter is not so easy, either. This sort of setup makes the SB220 safe to run 2000-Watt AM peaks or more.
Doesn't make it a good idea.
73
Shadetree Mechanic
Delaware Base Station 808
Good stuff! I will putting this in my notebook. You keep dangling carrots in front of me, eventually I will get the whole scoop.One modification that reduces the heat stress in "SSB" mode is to replace the factory-original 5.6-Volt zener diode with a series string of thirty (30) 3-Amp rectifier diodes. Each one provides about 2/3 of a Volt of bias. Thirty of them in series adds up to about 20 Volts. This reduces the zero-drive tube current so that the tubes only push about 30 Watts of heat apiece with no drive. This leaves some margin for running AM in SSB mode without melting the tubes.
It's no big trick to build from perfboard. We make a DIY version, but there's more to it than just this alone.
Reducing the tubes' idle current will now change the input impedance of the tubes. The SWR on the amplifier's input when it's keyed will rise if you install this trick by itself.
We install this input-matching circuit directly under the tube sockets for a customer who wants an 11-meter only AM hot rod.
To make room, we move the fat blocking cap from where it was over to the input pole of the relay. Makes sense to also replace the coax feeding from the relay to the tubes' cathodes with teflon coax if you have it on hand. The capacitor on the input-side of the coil is 68pf at 2500 Volts. The output-side cap on the coil is 47pf at 3kv. A lower voltage rating would be vulnerable to breakdown if you get the tubes too hot and one of them arcs inside. The coil is 7 turns on 1/2-inch diameter, spread for lowest input SWR.
Beefing up the parasitic chokes is also a big deal. The harmonic current in the tubes will be higher running hot-rod AM, and overheat the stock parasitic chokes. We use three 100-ohm 5-Watt resistors in place of the original single 47-ohm 2-Watt carbon resistor.
There are additional measures to take that beef up other weak links in the chain for hot-rodding the SB220. Bypassing the band selector's output side works best if you tap the output coil one turn farther down from the original 10-meter tap point. This compensates for the stray inductance of all those wires on the band selector. Using the original 10-meter tap point may increase the Q factor of the output circuit in a way that makes the tubes run hotter than necessary.
But that's enough for today.
This is one of those "You just gotta want to" modifications. Trying to justify the cost by how much higher you'll drive up anyone's S-meter is not so easy, either. This sort of setup makes the SB220 safe to run 2000-Watt AM peaks or more.
Doesn't make it a good idea.
73
552fl,
Nomad just told you what BBI doesn't/won't show.
More to it than tuning for Max Smoke.
Good Luck
73's
David
Nomad just told you what BBI doesn't/won't show.
More to it than tuning for Max Smoke.
Good Luck
73's
David
BJ radionut
Supporting Member and 6m addict
Yes and that one vid he did...was driving that amp with like 300w carrier...
Doing it that way all I can say is:
NFL
Doing it that way all I can say is:
NFL
Hate to hear that 552fl. The Heath is a great looking CLASSIC!
You could start talking on SSB? or using it on the CW mode only -tuning for Max modulated RF? I doubt anyone would be able to tell the difference in their S Meter reading-but I HAVE BEEN WRONG BEFORE!
Your Texas Star 500, if driven with 100 watts carrier would sound the same. Because the way that you are running it now ("modulated" power only as the driver) it may be slightly cleaner than the Heath. Same principle as Nomad was trying to convey with the Heath tune up method, I believe.
Good Luck to you. I hope you get your investment back out of it.
73's
David
You could start talking on SSB? or using it on the CW mode only -tuning for Max modulated RF? I doubt anyone would be able to tell the difference in their S Meter reading-but I HAVE BEEN WRONG BEFORE!
Your Texas Star 500, if driven with 100 watts carrier would sound the same. Because the way that you are running it now ("modulated" power only as the driver) it may be slightly cleaner than the Heath. Same principle as Nomad was trying to convey with the Heath tune up method, I believe.
Good Luck to you. I hope you get your investment back out of it.
73's
David
thank you david,
im going to try to get most of what I paid for it back..
im going to try to get most of what I paid for it back..