Amateur Radio Courses


#1

If anyone is interested in becoming a licenced radio amateur or just learning enough about electronics to be able to, the Gloucester Amateur Radio and Electronics Society holds courses at their meeting place, Churchdown School, Gloucester. The club meets every Monday evening from 7:30pm. For further info please contact me or come along to a meeting. http://www.g4aym.org.uk/training/default.htm

Dave Miller
G4HJV
zeddee@gmail.com


#2

My eldest and I are signed up for the next foundation course in October :slight_smile:

In other news, I’ve managed to collect together all the parts of the hackspace’s 2m/70cm antenna. Would anybody happier with being up ladders than me be interested in helping to install it? I reckon we can fit a nice wall socket thing so folks can plug transceivers in and get some reasonable range out of it.

Next project: Hackspace APRS beacon/digipeater/iGate? :slight_smile:


#3

Excellent news Alaric.


#4

I’m on holiday next week but the week after I can help get the antenna up. I can also bring my 2m / 70cm rig to get Hackspace on the air.


#5

I can bring a receiver, so if we don’t get any responses to a CQ, we can still see if it’s working.

Now, the antenna has a length of mystery coax dangling from it; I presume the thing to do would be to drill a hole through the wall and put a nice box on the other side with a suitable connector on it - I gather BNC isn’t the best thing at VHF/UHF frequencies, can you recommend a good connector? I’ll see if I can buy something suitable in advance.


#6

Before positioning the antenna it would be a good idea to test it. If it has been outside chances are there is some corrosion in the connection to the antenna. Check the state of the connection visually first. There should also be a dead short between outer and inner conductor. The connection housing may also have a trimming capacitor inside.

If you introduce another join through the wall you have 2 more places to weatherproof. I would recommend taking off the existing connector, feeding the cable through the wall and sealing it inside and out. An exterior connector is just providing another point at which corrosion can occur. The best solution would be a bulkhead feedthrough plate to provide weather proofing.

The connector to use for VHF is the PL259. I have a stock of these. Is there any marking on the cable to say what type it is? It should either be RG-58C/U (50 ohm) which is about 1/4" dia or if we are lucky, low loss RG-213, which is about 1/2". I have different PL-259’s for whichever cable it is.


#7

Yeah, a socket on the inside is what I meant - with the cable stuffed through a hole with a liberal smear of silicone to keep water from following it through!

I don’t think the antenna has been outside, from the look of it. I think it’s a Diamond X-200N from memory, I’ll take a look at the coax tonight!


#8

The cable is about 1/4" diameter; the writing on it just seemed to be all about how wonderful it was and that it’s got a 50 ohm impedance.

What I forgot to write down was the diameters of the tubular mast sections that need joining together, as there’s no U-bolts. But Screwfix is open until 8pm, so when I get there on Thursday I’ll work out what’s needed and go fetch something suitable!


#9

How do people feel about fitting a Raspberry Pi equipped with an RTL-SDR and a wideband antenna in the space, leaving it permanently powered and locally or remotely accessible using rtltcp?

My uses would be things like picking up Mode-S signals from aircraft, for high altitude balloon tracking, or for long-range LoRa experimentation.

Chris


#10

Sounds an excellent idea. There’s lots that can be done on a receive only basis, with no need for a transmitting licence. Just need to isolate it from any transmitting we eventually do.


#11

If we can get some spatial separation, that’ll probably be good enough unless you’re talking about transmitting oodles of power. I understand the plan is to have the radio installation at the rear of the space so putting the receive–only on the front would probably work quite well. It would only need a power connection and we could run wifi into the network so no real need for cabling and we can keep the RF cables small and short.

I’m tinkering with a bicone antenna for 400MHz upwards at the mo. I can make some standard dipoles for specific frequencies too depending on space and I have a PIN diode RF switch that could controlled from the Pi too. I think it has four inputs. I’m sure I’ll have a Pi1B or Pi2B somewhere and a RTL dongle I can donate.


#12

Any 2m transmitter I suggest should be limited to 10W max. RF energy and computers don’t mix.


#13

Given the interest in various receive-only applications in various bands, we might be able to rig up a tx/rx relay on the 2m/70cm antenna and have a preamplified 2m/70cm feed to anything that needs it, that cuts out when something transmits… And for v1, just manually unplug the receiver(s) to plug in the transmitter when using it and put it back afterwards. That has the advantage of making it harder for unlicensed curious button-pushers to accidentally transmit :slight_smile: