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Sunday
Sep032017

DMR Radio

A little while ago a friend of mine, a fellow amateur, spoke to me about getting into DMR. Him and another friend were welling to loan me a radio and hotspot to get me on the air. Well in the last week they sent me the equipment. After a few issues with my Windows laptop I finally got it up and running and Saturday afternoon was the first time I was on the air. 

I'm currently using a DV4mini and a TYT MD-380 DMR radio. With this handheld radio I can sit in my lounge room and talk to anyone around the world. Today (Sunday) I sat and listened to people from Canada, Malta and of course Australia and all while using a handheld and a USB dongle. It's amazing what you can do with these days. 

I must say, so far I'm enjoying it. I will have to be more active in the coming week while I'm still getting used to how it works. Digital radio I've never played with until now. Every time someone speaks the radio displays their information like call sign, name, location and DMR ID. So even if you don't hear the call sign the radio will display it for you.

 

DMR = Digital Mobile Radio

Wednesday
Jul052017

Remote Antenna Switch

A couple of months back I built myself a remote antenna switch so I could change antennas without having to go outside and manually change antennas. This switch was to allow me to switch between my vertical dual band VHF/UHF antenna and my VHF beam. The switch was made from 4 relays with would switch between antennas.

Well after a lot fo testing and a few issues I've now found that the relays are not good for use on the VHF or UHF bands. The remote switch work great on HF frequencies but nothing higher than about 50MHz. After that the VSWR rises too high, around the 2.1 mark. On HF the VSWR is perfect, 1.1.

So now I have to rethink the way I remotely change antennas. I now have to look at costly coaxial relays. These can cost upwards of $200 plus. So for something I thought I coudl build it turns out I can't, well not with the type of relays I've used. I now have to save money to be able to purchase a coaxial relay. For my planned VHF/UHF antenna system I'm going to need two of these coaxial relays. This will allow me to switch between my vertical dual antenna, a vertically mounted yagi and a horizontally mounted yagi. I just won't be able to have a spare output for when I'm testing an antenna but I can work around this anyhow.

I love working on the VHF bands but when it comes to bulding these type of things the band can be very hard unlike the HF bands where it's much easier. The fun and games when playing with radio frequencies :)

 

Wednesday
Apr192017

The Work Continues

The work continues on my antenna system. Over the Easter weekend I had a friend over to help me pull down my 2m yagi antenna and do some work on the mast. I have been able to get it up a little higher. 

Since doing all the works like changing the coaxial cable, rebuilding the remote antenna switch and now getting the antenna up about a metre higher I'm able to key up the Robonvale 2m repeater, almost 24/7. This repeater is about 80kms west of my QTH and I use to only key this repeater when there was good tropospheric ducting around. My VHF antenna system has been a big headache for me. First it was the loss of range and then a VSWR issue. The biggest issue was coaxial cable losses, losing almost 20 watts in the coax was a big eye opener and then my remote antenna switch I had more losses. A redesign fixed that issue and replacing the coax with very low loss coaxial cable dropped the losses from 20 watts to just 2 watts. 

Over the last few months of going through all the issues I've learnt a lot when it comes to feed line losses. It's made me not just redesign the remote antenna switch but also redesign my antenna connection box. It's even made me rethink the replacement works for one of my CB antennas. I'm now not just replacing the damaged antenna but I'm going to replace the coaxial cable for both my 27MHz and UHF CB antennas with low loss heliax cable. It might be a little over kill for CB antennas but while I'm doing the works I may as well do the job fully. 

Oh well the work never stops :) 

Monday
Apr032017

Hard Work Pays Off

Over the last couple of months I've been doing a lot of lot on my VHF antenna system. After I found I couldn't talk to someone 15kms out of town I had to find out what was going on. I knew I used to be able to talk a lot further than 15km outs and the only thing that had change was I added a length coax. I added this length to make way for my tower, so this extra length was needed. 

I had to ask for help from a good friend and they got me to do a couple of tests. These tests found I had a lot of losses and as anyone would know, any power loss will also effect receiving. I had an amateur radio friend offer me some good coax, LDF450 which was being removed off a couple of sites he was doing work at. I replaced the RG213 with a length of LDF450 and noticed the losses power improved greatly. I've now replaced the last of the RG213 with LDF450 and the change was big. The only issue I was having was with my remote antenna switch. So I did a bit of looking around and noticed all the commercial ones were made of plastic and not metal. I thought this was clearly important so it was sit down and redesign mine. I got a plastic box big enough to house everything and changed where the connectors were placed. Again this change has improved things again. Not being an expert but I think the metal box was interfering with the VSWR. So with it now in a plastic box this won't happened. I have even sat down and redesigned my antenna connection box and have made changes to that. 

This whole thing has been a little stressful. I still have a bit more to change but this will happen slowly. I'm currently happy with the progress of things. I'm hoping to have a helper here at Easter so I can make some non-costly changes to my 2m yagi antenna. I'm hoping to get it up a little higher and change the coax I'm using to some 1/4 inch Heliax coax I have here. I'm also hoping to use the same coax on my 27MHz CB antenna and UHF CB antenna. Currently the 27MHz antenna is using RG58 and the UHF I'm using over 30 year RG213. I need a friend to help with work on those two antenna, I need a forklift and a couple of hours of his free time. 

There is always work to be done. Hopefully one day I will be able to get my tower up, again I need help from others. I'm very thankful for those that have helped me out with cable and other bits and pieces that has made all these upgrades and changes possible. As with them there is no way I could afford to replace the coaxial cable with the coax I've used. The LDF450 coax is worth a bit of money, I've seen it for about $10 to $15 per metre. This may not be much for some it's a lot of money for me. The connectors for this type of coax are not cheap either, about $20 to $40 each. Again I've been lucky enough to get the connectors for free. Anyone that says amateur radio operators are not helpful and are up themselves clearly are hanging around with the wrong ones. I've got one that's gotten me in with Broadcast Australia and another one who I had never meet and only spoken to over FB, go out of there way to help me. Of course there are some bad ones out there and yes I've meet them but there is so many more out there that out number the bad ones.

Amateurs are wonderful people. 

 

Wednesday
Mar152017

If It's Not One Thing, It's Another

As you will know, I've been having a few issues with my VHF/UHF antenna system. Well since my last post I've been able to change the coaxial cable from the antenna switch and antenna. I had a couple of little issues but I got the job done with out help. Mind you I don't think I'll be doing it again with out help. In saying that no one seems to want to help. I guess this is why my tower hasn't gone up, just can't get anyone to help and do the jobs I need to be done. It's like you can't rely on anyone. 

I have came up with another problem. I've been too busy worried about power losses in my system I haven't been checking the VSWR of the system. I have since checked this and found it was a little too high for my liking. My remote antenna switch is a part of the problem and the other is my antenna connection box on my mast. It's like I just can't get it right regardless of what I do. I guess you could say I'm not as smart as I thought I was. Story of my life.

Today I ordered a coupel of parts so I could change one part of the system, I really can't fix the other part of the problem as this would mean replacing my remote antenna switch with a purchased one. To purchase one would cost me about $300 delevered and I don't have that amount of money laying around. So it looks like I'll just have to put up with it and see how it goes. I'm just adding it to the list of stuff ups. I've replaced all the RG213 I had in the system with LDF450 and I've been able to remove the large losses but I just can't seem to get everything right. 

When I was redesigning and building my microphone/PTT switch I was having issues getting it to work fully. I ended up put it in the draw for a couple of months hoping having a rest from it might help. After a the time away I was able to bring it back out and find the problem within minutes. I think it's time to do the same thing, walk away from the radios for while and come back to it after a break. I think this might help again. So I think I will leave the radios off for a while and come back to them later. I can only try it and see how I go. It can't hurt anyone.