Proper attenuation for Pure Sig from output of Amp

Skip KE9L
Posts: 2
Joined: Sun Apr 09, 2017 4:51 pm

Proper attenuation for Pure Sig from output of Amp

Postby Skip KE9L » Wed Jul 05, 2017 4:00 pm

Hello All,

Have a couple of questions about proper attenuation for Pure Signal from the output of an amp. I have been having some problems with that while using a CleanRF sampler.
1. I am wondering if I have damaged my receiver, if so how can I check that?
2. Will PS work with too much attenuation?
3. Recommendations for a better sampler?

Thanks Skip KE9L
User avatar
W1AEX
Posts: 147
Joined: Sun Apr 09, 2017 6:17 pm
Location: Connecticut, USA
Contact:

Re: Proper attenuation for Pure Sig from output of Amp

Postby W1AEX » Wed Jul 05, 2017 4:58 pm

Hi Skip,

1. I'm not sure which ANAN you are using but I believe the return path for PS is through RX-1 on all of them. If your unit is a 100D, 200D, or 8000DLE then you can check for damage by tuning to a signal with RX-1 routed through ADC-1 and then tune to the same signal using the same antenna with RX-2 routed through ADC-2 and if you see no difference in strength then things are probably fine. If the signal through RX-1 is significantly weaker then you may have an issue. If you have one of the rigs using a single ADC (ANAN-10 series, ANAN-100, ANAN-100B) the same test might work, unless the ADC itself is damaged, which in that case would affect both receivers.

2. Yes, PS is robust enough that it will work with too much attenuation but not optimally. The Auto-Attenuate feature pretty much guarantees the perfect amount of attenuation assuming that your return sample is arriving at somewhere between -63dBm to -53dBM.

3. The gold standard seems to be the Xtronic XDC couplers built by Dave - AC2IQ which easily handle full legal limit. The current XDC-4 series samplers are sold by HRO for $150. They are flat across the spectrum used by the ANAN rigs and work perfectly with PS. Additional attenuation is required for the -43dB return port so an additional -10dB or -20dB pad is required inline between the sampler and the ANAN. Those are also sold by HRO for 11 bucks.

73,

Rob W1AEX
"One thing I am certain of is that there is too much certainty in the world."
User avatar
w-u-2-o
Posts: 1235
Joined: Fri Mar 10, 2017 1:47 pm

Re: Proper attenuation for Pure Sig from output of Amp

Postby w-u-2-o » Wed Jul 05, 2017 6:42 pm

Skip,

Everything you need to know about how to calculate the optimum amount of attenuation is right here in this thread.

The CleanRF sampler is not up to the task of providing good feedback for PureSignal. I bought one way back and I'm sorry I did, and I can't in good conscience bring myself to sell it to anyone else. It's plenty fine for feeding a scope, but for any serious purpose, like running PureSignal, it is completely inadequate. Its gain flatness over frequency on the coupled port is terrible, it's adjustment not repeatable, nor marked, and its large adjustment range leaves you quite vulnerable for damage to your radio.

The claimed adjustment range on the CleanRF 5K "sampler" is from 26 to 50dB of attenuation. 62dBm (1500W) - 26dB = 36dBm, or 4W! If you accidentally did that, it's quite possible you hurt something. You would know because your radio would be deaf on RX1. The first device in the chain that is very sensitive to high RF power level is the 31dB step attenuator and it's maximum RF input rating is 30dBm or 1W. Rob's suggestion of checking performance against RX2 is a very good one!

At 1500W and 26dB coupling factor you need at least another 30dB of attenuation. At 50dB coupling factor you need at least another 6dB. That's a huge range, and all it takes is one little bump of the adjustment on that CleanRF unit and you could cook something. You could go with the 30dB of extra attenuation and turn the coupling factor to maximum (26dB), that way if you accidentally bumped it power levels would only go down, not up, but you'll find that you still have problems because the CleanRF design does not provide exactly 26dB on every band.

I'd strongly recommend you either buy an Xtronic brand coupler, as Rob already suggested, or build a proven design from scratch.

73,

Scott
Skip KE9L
Posts: 2
Joined: Sun Apr 09, 2017 4:51 pm

Re: Proper attenuation for Pure Sig from output of Amp

Postby Skip KE9L » Sat Jul 08, 2017 11:23 pm

Thanks Rob and Scott, will check the receivers this weekend and will purchase the XDC-5 when it becomes available. Will post what I find on the receiver.

Skip KE9L

Return to “PureSignal Operations”