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AirSpy HF+ D1

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sm6fhz
Posts: 169
Joined: Wed Aug 19, 2020 3:21 pm
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AirSpy HF+ D1

#1

Unread post by sm6fhz »

Hi All.
Does anyone have a schematic or maybe knowledge about what the "D1" component at the HF RF-input has as type designation?
It is placed in the very close vicinity of the input connector as the very first component after the HF input connector.
I suspect that it was (partly?) damaged during a thunderstorm where we had a lightning stroke just around 50 m away from the antenna (a short vertical wire).
The HF+ is working, but with reduced sensitivity / gain / noise floor. Particularly at lower frequencies.
73 / Ingolf, SM6FHZ

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KA1GJU
Posts: 144
Joined: Tue Aug 11, 2020 2:16 pm

Re: AirSpy HF+ D1

#2

Unread post by KA1GJU »

Usually I see two, back to back such as this on page 11:
http://www.na0tc.org/lib/exe/fetch.php? ... rotect.pdf

I use the following on my RX antennas that are somewhat near my two HF remote base TX/RX antennas, they also supply a little protection from a nearby hit. They even provide the schematic:
https://www.arraysolutions.com/as-rxfep

For an accurate part number/specs, you may want to post over on the Airspy groups.io site:
https://groups.io/g/airspy

73 Kriss KA1GJU

jdow
Posts: 456
Joined: Mon Aug 10, 2020 8:17 pm

Re: AirSpy HF+ D1

#3

Unread post by jdow »

Lemme see here. 4kW is about 500 volts RMS in 50 ohms. Call it "less than 1000 volts" with some mismatch. So a 1 meg 1 W resistor can be safely put across the antenna input to the house. 250 k 1 W is probably suitable for less demanding (i.e. within legal limits) operation. The intent is to safely bleed off static electricity without blowing out the bleeder resistor. Dipoles and verticals will benefit from this. Folded dipoles, gamma or T match beams, and the like don't need this - most of the time. If you disconnect the coax at the antenna during maintenance having that resistor may save something when something with a static charge touches the now free floating antenna input. (You can probably do "well" with a 5 K 1/10 W resistor if it is mounted across the receiver input. Personally, if I lived in a high lightning area like Dallas Tx or Florida, I'd use both plus gas discharge plus suitable shunting diodes. In the 50+ years I've been living here outside Los Angeles (shudder) I've never needed protection. A thunderstorm consists of a sudden BOOM, three to a dozen smaller booms, and silence. BOOM is preceded by a flash and 2 or more seconds of silence.)

Oh yes, another thing I did is added impedance to the lightning path into the house. I put one or two turns a foot or so in diameter into the feed line just before it went into the suppression such as I used. I'll gladly take a few extra dB of protection if it comes basically for free.

{^_^}

Homer1952
Posts: 9
Joined: Wed Aug 19, 2020 11:21 am

Re: AirSpy HF+ D1

#4

Unread post by Homer1952 »

Ingolf,
Have you measured D1 to see if there is any DC leakage? Then check it for inductance & capacity. For replacement of these I use the same diodes used in the Icom R75, 1SS302. They are very fast devices.
Unfortunately many SDR OEMs do not post schematics/ service manuals.

Good luck with the repair - Bob W8RMV

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