RSP-1 as a bat receiver?

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radiogareth
Posts: 6
Joined: Wed Jan 06, 2016 10:28 am

RSP-1 as a bat receiver?

Postby radiogareth » Wed Sep 06, 2017 7:21 am

My wife and I went on a bat walk last night and were lent a simple bat RX that tuned from 20KHz to over 100KHz. Inevitable I thought I'd try this, realising that my RSP will receive down to 10KHz. Has anyone any advice on what to use as an aerial? I'm thinking ultrasonic transducer, piezo tweeter from a loudspeaker etc. Will I need some matching or pre-amp? Could be a whole new market for RSP's. watching the WHOLE bat spectrum would be easy.....
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WA2AKV
Posts: 2
Joined: Sun Sep 24, 2017 7:17 pm

Re: RSP-1 as a bat receiver?

Postby WA2AKV » Mon Sep 25, 2017 4:49 pm

Excellent idea old man. When I was 12 years old in 1962 I built an "ultrasonic sniffer" from a circuit in Popular Electronics. The input to this device were audio frequencies in the range of 20-60Khz, the output was in the human audio range. Today there are various "transducers" that can be used for the "aerial" as you say - just Google 'ultrasonic sensors' that should get you started. BTW I had the same idea as you just a couple of days ago after a visit to Austin Texas after visiting the Congress Ave bridge and the nightly bat swarm.
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WA2AKV
SOTA QRP and other radio interests

g1hbe
Posts: 354
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: RSP-1 as a bat receiver?

Postby g1hbe » Mon Sep 25, 2017 11:14 pm

I've built a few bat detectors and the difficulty is always the transducer. Some electret mics will reach up to about 20+KHz but most bats operate above this. Then there are the cheap 40KHz transducers that work well but their response is quite narrowband and they only pick up in the range of maybe 37 to 43 KHz. I'm using one of these at the moment and although I do hear the odd bat in the evenings, I am aware that I'm probably missing most of the action.
Some people say that piezo tweeters work, but I've never found one that does!

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Andy

radiogareth
Posts: 6
Joined: Wed Jan 06, 2016 10:28 am

Re: RSP-1 as a bat receiver?

Postby radiogareth » Tue Oct 31, 2017 10:38 am

I was hoping that a tweeter of some sort might do the trick but they aren't designed to operate at those frequencies so its a bit hopeful. Maybe the really old ultrasonic units work better, ie less narrow-band. I think I have a pair somewhere unless they got culled in the recent 'retire and tidy up life' tasks.....
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dejong2017
Posts: 1
Joined: Wed Sep 19, 2018 2:41 pm

Re: RSP-1 as a bat receiver?

Postby dejong2017 » Wed Sep 19, 2018 2:47 pm

I had the same idea and went ahead to try this. I found someone posted this on the RTL-SDR board.
Find the link : https://www.rtl-sdr.com/detecting-the-s ... lay-rsp1a/

the link to my short video on youtube is here proving it works. https://www.youtube.com/watch?v=sKtn_zHfUqw&t=3s
let me know if you need further information, would like to improve this type of sensor for taking a peek in the unknown world of high frequencies.
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g1hbe
Posts: 354
Joined: Sat Jan 17, 2015 3:28 pm
Location: Cheshire, UK

Re: RSP-1 as a bat receiver?

Postby g1hbe » Wed Sep 19, 2018 10:24 pm

My detector is a self-contained one with a pre-amp, mixer and audio amp driving a small speaker. There's high-pass filtering in the pre-amp and low-pass in the audio amp so there's no 'howl round' from speaker to mic. The local oscillator is tunable over approx 15 to 40 KHz.
I've recently found a random electret mic in the junk box and it seems to work up to about 35 KHz. Sadly it has no markings so I can't identify the type. It is a bit smaller than the usual 10mm dia ones. Of course testing these things is subject to error as you need a 'known good' transmit transducer on the output of your signal generator!
Most of the bats I hear around here make rapid tick-tick-tick sounds, and the repetition frequency increases as they get closer to objects, at least I assume that's what I'm hearing. The other night I heard a new type - it was a number of bursts of very rapid 'ticks', like a brrrr-brrrr-brrrr.
It's been a pretty quiet Summer for bats around here, I've only heard activity on three evenings.

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Andy


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