Watt meter is not broken or tinkered with, and it was bench tested at 185 watts at the radio shop. I am sure the Galaxy dx959 is over driving it though.
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Losing receive with amp connected
- Thread starter ShadowDelaware
- Start date
Shadetree Mechanic
Delaware Base Station 808
It is super clean, a nice desk piece if nothing else.
The preamp kills your receiver signal when it's turned on? This is not the fault of the relay. It's a blown preamp circuit. The preamp is built to amplify tiny signals, micro Volts. The output of the radio's transmitter is many thousands of times more voltage than that.
When you key the mike, the relay takes a short time interval to physically move from the off position to the on position. During this delay, a short burst of the transmitter's output energy is being crammed up the anus of the preamp circuit. A circuit meant to handle tiny voltages. What keeps this from blowing it up is the shortness of this brief burst of transmitter energy, while the relay makes up its mind. Typically between 10 and 20 milliseconds.
Sooner or later someone flips the "SSB" switch and keys the mike on AM. The "SSB" switch introduces a capacitor to the RF sensing circuit so it takes longer to drop back to receive side.
Just one problem. It also delays the time to respond and go "click". That delay pumps more transmitter energy into the hind end of the preamp circuit and blows it out.
Sooner or later.
Unless you swoon at the thought of using the receive preamp, I would just ignore it and declare victory. If it worked, what it would do is make the noise level louder. Not worth digging into the preamp circuit to fix.
73
When you key the mike, the relay takes a short time interval to physically move from the off position to the on position. During this delay, a short burst of the transmitter's output energy is being crammed up the anus of the preamp circuit. A circuit meant to handle tiny voltages. What keeps this from blowing it up is the shortness of this brief burst of transmitter energy, while the relay makes up its mind. Typically between 10 and 20 milliseconds.
Sooner or later someone flips the "SSB" switch and keys the mike on AM. The "SSB" switch introduces a capacitor to the RF sensing circuit so it takes longer to drop back to receive side.
Just one problem. It also delays the time to respond and go "click". That delay pumps more transmitter energy into the hind end of the preamp circuit and blows it out.
Sooner or later.
Unless you swoon at the thought of using the receive preamp, I would just ignore it and declare victory. If it worked, what it would do is make the noise level louder. Not worth digging into the preamp circuit to fix.
73
I have a Cobra 150 amp, and the pre amp on it randomly works. Switch is fine, but its very tempermental. I hardly use pre-amp anyways, so didn't care to look into it to even try and fix it.
The biggest issue was that I had zero receive at all with the amp powered off and no power to the antenna at all with the amp off, after cleaned the contacts both issues went away and just the preamp doesn't work now. To me that is fine all it did was raise the noise floor anyway. I am still learning and appreciate all the information I have received. Everyone is more than helpful and it is greatly appreciated I love absorbing the knowledge.
Shadetree Mechanic
Delaware Base Station 808
The best part about being here is that people are willing to share their knowledge, all a person needs is a desire to learn. I have learned a lot during my short time here.
Desire to learn, humility, modesty and some thick skin. These boys 'round here CAN be brutal, but that's usually the exception and not the rule. It's like a big family, assuming you can get invited to the reunion.
I generally keep my voltage to 14 volts max just to be on the safe side. You may see a few more watts with 15 v versus 14, but not enough to make a difference on how well your signal is received, and the transistors in the amp will be much happier, and will live longer lives running at 14 volts.
Just my 2 cents worth, and I realize lots of people overvolt stuff just to gain a few watts.......
It's 4 cents worth.
It's a mint old amp with very expensive stud mount transistors, be kind to it.
73
Jeff
The crazy thing is I can't find any data sheets or anything about the transistors online. I definitely can not find the transistors themselves.
They are basically a Motorola MRF 455, the A suffix means there is a single stud mount in place of the 2 bolt flange, rare today.
Here is a picture of a 455 and a 450A from rfparts just to show the mounting.
73
Jeff
Here is a picture of a 455 and a 450A from rfparts just to show the mounting.
73
Jeff
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