Beginning Meteor Detection

[eliot]

I am completely new to radio astronomy (and Ham Radio in general).  I have put together a simple meteor detection system consisting of FunCube Pro+ Dongle and an off the shelf 4 Element Yagi Antenna (2m 144MHz-146MHz).  I'm following the S@N article, some other material on the BAA website, and https://stargazerslounge.com/topic/220150-new-to-meteor-detecting/.

I'm working on a Mac (because I want to make my life as hard as possible!).  I have managed to install the Mac version Qthid 4.1 and got Spectrum Lab V2.92 working under WINE / PlayOnMac.  My antenna is vertically aligned and pointing SSE.  I have connected the antenna to the dongle via a 9m lead with a SMA connector.  The dongle is attached to my Mac via a 1.8m USB extension cable.  Setting Qthid to 92.5 MHz (Qthid 4.1 appears to work in MHz not kHz) and using Spectrum Lab's audio output I can play a very crackly Radio 4 through my Mac's speakers.

The worrying thing is disconnecting the antenna cable from the dongle the reception is about the same.  Is this normal (this is where I feel like a new dad again)?

I re-tuned to 143.048 MHz and loaded the MetScat_starter_v1.USR configuration and waited a 10-15 minutes to see if I could see any meteors on the screen.  Nothing showed up - obviously we are nowhere near a meteor shower and only sporadic meteors will be around at this time.

A few things to note (I think most of this is clutching at straws as Radio 4's signal should be so strong):

• The antenna is 2m high off the ground sitting adjacent to a uPVC conservatory, but has clear line of sight South East and South.
• I brought the antenna in to the conservatory change the orientation to horizontal and rotated the direction it pointed.  I could not improve the Radio 4 signal by doing this only match it's performance outside pointing SSW.
• The antenna cable is not of the best quality and does not have many strands.
• The antenna cable goes past my TV, but the dongle is about 2m away from the TV and laptop.
• The antenna has a tuning capacitor on the connector this appears to have no effect on strengthening the Radio 4 signal.

(This setup is only temporary whilst I try to get the system working.  I would eventually like to attach the antenna to the chimney, and I have a micro PC that I could run Ubuntu on in the loft).

I'm sure I've missed something very simple or have completely misunderstood the setup somewhere.

[wxsatuser]

Where is the nearest R4 transmitter to you on 92.5?

The nearest most powerful one that I can see is North Hessary Tor at 160kw with mixed polarisation.

Would assume most are to weak for your 2metre yagi.

[eliot]

Yes sorry I should have updated my location.  I live in Calne Wiltshire so I pretty much have a transmitter sitting on top of me.

To be honest I didn't look up the frequency of R4 I just looked around that area of the spectrum and the only frequency where I can hear voices is 92.5MHz.  Having now looked up Calne's R4 frequency it's 92.6MHz.  Tuning Qthid to this I get string stronger signal just no voices.  I quickly checked published R1, R2, and R3 frequencies that are also broadcasted from this transmitter and I do find I get a signal if a lot weaker.

Please see below my desktop

[The Admiral]

Try tuning to 144.43MHz, the frequency transmitted by the VHF beacon GB3VHF (http://www.gb3vhf.co.uk), and see if you can pick it up. That should be a useful test of system function without having to wait for a sporadic event.

I'm a bit surprised that there was no difference between antenna connected or not, though you were well away from the antenna's centre frequency. Incidentally, you are trying to pick up a signal close to the horizon, so your antenna may be a little low down unless you've a clear view down this far. I have my antenna horizontal (in the loft) contrary to the S@N article, and it works fine. Also, I can see no advantage in pointing the antenna slightly above the horizontal as the sensitivity pattern in the vertical plane in this instance is governed by the proximity of the earth rather than the pointing angle.

Good luck. It often takes a bit of fiddling to get things working, not helped by the fact that one has to 'tune in' to the Graves radar 'blind'.

Ian

[eliot]

Thanks Ian,

Another stupid question does the screenshot below show I'm receiving the GB3VHF beacon?

I suspect not given that unplugging the antenna makes no difference.

I'm going to make up better lead tonight, and sit up in the loft to see if I can get it working.

Thanks,

Eliot

[The Admiral]

Sorry Elliot, it isn't. The beacon is not, as you might reasonably think, a single CW carrier, but is a cycle of different signals, quite recognisable. You can hear the cycle here: http://www.gb3vhf.co.uk/GB3VHF.wav 

In order to hear an audio output I suspect that you'll have to de-tune by, say, 0.5 or 1 kHz in order for the carrier signal to be converted to an audible tone.

It's certainly worrisome that disconnecting the antenna makes no difference. The SMA connector is a tiddly affair and I use a properly made connector lead to convert it to a more sensible rf connector so that I can terminate my own co-ax feeder cable. I can receive the beacon with the existing alignment of antenna, as Oxford is on the beam centre-line, but you may need to direct yours a bit futher east to point to Kent. Try it without first.

Ian

Edit. I'm intrigued that the antenna has a tuning capacitor. What make is it please?