RF Sampler For Hermes Lite

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gareth

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Sep 15, 2024, 3:19:20 PMSep 15
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Hi everyone im looking to use pure signal with the hermes lite 2 and my amplifier at present is an RM Italy KL505 used on 10 and 11 meters only and max output of 250 watts. I have looked at this rf sampler and need to no if it is suitable for my needs, eventually maybe get a better amplifier but max output would be 400-500watts.  HF RF sampler (omni-rf.com)

Now i emailed the man about the sampler but he is not familiar with the Hermes.  Below is an email response from him but im out of my depth to answer. 

"I'm not familiar with the Hermes 2 but I assume that you have carried out a mod to enable it to use Pure Signal? If so, do you know what input level you need to give the pure signal input? I do have an RF sampler that could be used but it all depends on that magic input level you need. When placed after your final PA my -50dB sampler will give you a clean, sampled output at -50dB retaliative to the input power so if you're putting 500W in, the sample output will be roughly 7dBm. I may be able to create a custom sampler level depending on what you need."

So looking some advise on what he is asking or if its fine to go with his stock sampler linked above. Im in the UK and would like to order from the uk.

Thanks in advance.

GM8JCF

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Sep 16, 2024, 4:45:48 PMSep 16
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Hi Gareth

I use a -50dB RF Sampler https://symkrilag.uk/shop/rf-couplers/rf-tap-attenuator/500w-50db-rf-sampler-tap-attenuator/  only GBP 34.00 together with 2W SMA RF attenuators, https://www.ebay.co.uk/itm/404720474656?var=674718146662 around 3 for £12.  I have a selection of these SMA RF attenuators, and found that with my BLA-350Plus putting out 125W PEP, I only needed 6dB of attenuation and get very reliable PS operation.

Hope this helps

Peter - GM8JCF

Colin Larsen

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Sep 16, 2024, 5:37:01 PMSep 16
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Search for RF sampler down the page 

73
Colin
ZL2FL

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G4ZAL

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Sep 17, 2024, 4:08:54 AMSep 17
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I made my own by basically copying Didier's switchable coupler...

Nigel
G4ZAL

DL1YCF

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Sep 17, 2024, 8:44:10 AMSep 17
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There is one thing to note about the sampler for the HL2:

The main and auxiliary RF input are just tied together, so
a sampler with a „correct“ 50 ohm impedance will induce
a 3 dB damping of the normal input signal.

Therefore it is better to have a final pi-stage of the
sampler that has a higher output impedance (that is,
the resistor from RF3 to ground is larger than 50 ohm).



Frank Johnson

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Sep 29, 2024, 4:22:05 PMSep 29
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In this design:

The author has made the mistake of earthing the braid at both ends of the sampling line.
It should be earthed at one end only so the braid acts as a Faraday shield.
His will sample the current on the OUTSIDE of the line and give unpredictable results.

Frank

V85NPV

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Oct 6, 2024, 11:00:26 PMOct 6
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Hello ,

i guess some alternative design maybe available and will also work.

According the design i am using it works perfectly using Thetis or PIHPSDR . One side of the coaxial Braid is NOT connected to the Ground/earth directely but connected to a 50Ohms Resistor . i have tried few but since this one is working decently and i can run this coupler after my Power Amplifier which is about 600w Max . If you are using more power just adjust one of the resistor linked to the rotary switch. This coupler is connected to my System for years now.

Best 73s Didier V85NPV
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