Did I really just do this...

[Napalm]

I've built myself an 8 port multi coupler. Everything is good quality surplus or new stuff. Filters, bandpass, notch, RF limiter etc.

I was testing something today and connected an RTLSDR to one of the outputs, without realizing I had Bias-T power turned on.

I now have a sneaking suspicion I fried something on the output of my ZHL-2010. Signals appear down compared to before I was an idiot but I'm doubting myself - the local fire tone out usually gives me -30dBm with the amp in line but now it's -55dBm.

This one is probably more for @prcguy than anyone else, but you all can laugh at me too.

Is this going to be fixable? I probably applied what, 3.8v at a couple of hundred mill amps up the spout of the ZHL.

I was SO careful to protect the INPUT of the amp I completely forgot about the idiot in the shack 😂😂😂😭

David

 

[prcguy]

Why would you think I would have any info on this?

Was the bias T voltage applied to the 8-way divider or directly to the amplifier output? I just took apart a ZHL-2010 and it has no continuity between the output RF connector and ground, its in the multi megohm range and appears to have a series coupling cap between the connector and active output device. There is also an RF choke or transformer or ?? that may be between the coupling cap and connector but its buried in goop and I can't see enough detail. In my opinion a moderate voltage applied to the output connector of the ZHL-2010 should not cause a problem.

However, if you applied the voltage to the output of a divider they are all a little different with some having transformers and others having resonant length lines with resistors bridging the outputs. Voltage applied to a divider could cause damage to some.

I would test the amplifier without the divider and you should have about 9dB more signal out of the amp than the 8-way divider after it.

Here is a picture of the output section of a ZHL-2010 with the RF output connector on the right.

 

[prcguy]

Looking at the data sheet for the HELA-10 amplifier used inside the ZHL-2010 its got a symmetrical output bridged together with a transformer and .01uf series capacitors at both outputs.

 

[Napalm]

Why would you think I would have any info on this?

Was the bias T voltage applied to the 8-way divider or directly to the amplifier output? I just took apart a ZHL-2010 and it has no continuity between the output RF connector and ground, its in the multi megohm range and appears to have a series coupling cap between the connector and active output device. There is also an RF choke or transformer or ?? that may be between the coupling cap and connector but its buried in goop and I can't see enough detail. In my opinion a moderate voltage applied to the output connector of the ZHL-2010 should not cause a problem.

However, if you applied the voltage to the output of a divider they are all a little different with some having transformers and others having resonant length lines with resistors bridging the outputs. Voltage applied to a divider could cause damage to some.

I would test the amplifier without the divider and you should have about 9dB more signal out of the amp than the 8-way divider after it.

Here is a picture of the output section of a ZHL-2010 with the RF output connector on the right.

View attachment 194094

Because you always recommend the ZHL and I figured you'd have the info. I was deferring to your vast knowledge on most things LNA. No sarcasm just respect for your knowledge, friend.

Sorry to call you out specifically.

Thank you for taking the time to open one of them up for me. It was applied to one of the outputs of the divider (a Meca 809-2-0.252). I'll check it directly connected to the amp. Thanks for the hint!

My last two multi couplers I built, I zapped the amp in one by transmitting too close (hence the RF limiter) and the last amp died from a nearby lightning strike (it's protected now).

 

[Ubbe]

It was applied to one of the outputs of the divider (a Meca 809-2-0.252). I'll check it directly connected to the amp. Thanks for the hint!

Are you stating the correct model number? That's a power divider that goes up to 500MHz and can handle a 2W signal into one port.

/Ubbe