Skimmer! Crossband! Sdr!
Since last year Bill J68HZ said he wanted to do some skimmers to put up here in J6 Land. I agreed and we decided it was a go ahead. He built the skimmer from DX Engineering Equipment. The Hardware from antennae coming down is the following: two ARAH-1P Antennae, into a 2 port splitter/combiner by way of power injector module. From there it goes to a receiver guard and into a RPA-1 Receiver amplifier and into the QS1R Sdr radio. All this was nicely built into an empty dell pc case. Bill did a great setup of all the software on a dell pc on windows 7. He has had this on the ready for a while whilst we were looking for a good site to put it on. It cannot be in our shack since we would overload it if we so much as looked at a radio.
In came Lin J69CU, he came back to radio recently and we hooked up at some point. He got interested in the crossband setup I was trying to work on and from there we just started talking and of course I mentioned the fact we were looking for a good spot for the skimmers and crossband. The skimmers needed a good location and internet access and that was the harder part actually. But Len said for the both he had a perfect site in mind. I said ok lets go and see and try it out. We organized and the whole crew went to do a site visit. We met at Soufriere and went up to the base of Morne Tabac where we parked and gathered all our stuff to go up and try out. After a good 30 minute climb, going up a track in the forest and climbing 150 meters up. Once on site it was like WOW this is it! We setup a temp antenna on the tower on vhf and worked as far as St Kitts’ repeater. Simplex qso’s were done from there to all our qth’s up north without as problem. The only catch was internet was at least 3 km away!
After some good fun up on top we all climbed back down and we all agreed it was a perfect location! So now to find a way to get the internet up there.
However when I spoke to Bill that evening he was like you can see the far point directly? So yeah we could, then he said that is easy I will bring you the proper equipment for that. Which he did when he came down in April. Whilst he was there we were going to do the initial install of skimmer antennae together with the Crossband and a Sdr receiver. Aha the sdr, the side project once we started talking skimmer I started thinking I have a sdr radio, if we could make that accessible for the guys here?! So I started working on that. I used an old Dell 755 with Windows 7 as the base. The sdr is an Ensemble II RX only, a good little sdr receiver it is too! So got it going by using Sdr Console, with HDR and then shared out via Remote Hams. This worked very well once I had it setup at the shack. I had J66SJ Cyril and J69CU Lin test it out.
So back to the story, Bill was on island and we were going to do the climb, and Bill was climbing also! We decided on an early early climb, we met at the base 6:30 Am. The whole J6 Portable crew was present that day, I also brought along a couple of the cousins to help carry the load up. The plan was simple enough get up there, put the antennae up plug it all in and go down to the studio and hook up the other end and have it all running. Famous last words those were
We took our time getting up there, Bill had a bit of a challenge but he took his time and made us all proud by getting up to the top. Lin and myself climbed the tower and set about putting un the antennae for the receive and the wifi link equipement of course the Crossband antenna went up also. Once that was done we proceeded to setup the skimmer and the network connection in good time. We got about halfway of the Hardware setup when we decided that Bill and Lin would go down to Soufriere and start the setup of the link on that end.
Whilst we setup all the pc’s for the skimmer and the sdr etc hooked up all the cabling and tidied up all the cables, Bill got that link up and with a bit of back and forth of vhf we aligned the antennae just right. This gave us internet access at the site and the in principle the skimmer and sdr ought to be online. Everything was online but try as we might we could not get a clean receive. We all decided it was a day and we would analyze our situation and see via remote access what it did over a few days.
Via remote access I tried all sorts of stuff to get it to work but nothing doing it was “deaf” for now.
A fresh climb was in order, so Ian J66CD J69CU Lin and my self J69DS went up again. We tried all sorts of tricks to get it going but we were not very successful. However, we figured out that part of the issue were the radio and tv stations nearby. We had a nice group meeting with J68HZ Bill K0UM John, J69CU Lin and myself trying to figure what the solution was. Bill decided on doing a design of filters to add inline.
Lin on return to his qth set out to find some fm band filters and found one that claimed 80 db and a RS one that did 20 db. He got one doing 80 and 4 20 db filters. Of course this meant going back up! So we did a climb the following week to add in the fliters. We added the 80db right before the receiver guard, which did bring down the interference. We also added a 20db on each incoming antenna. We were still getting something. So we removed the pre amp thinking maybe it was over amplifying the signals. That did not make much of a difference. We checked then decided to check the noise level on the power supply and low and behold that thing was noisy. However, with a bit of grounding and filtering we got it to acceptable levels. THE SKIMMER WAS ONLINE!!
However no matter what we tried with the sdr I was getting pure noise. So We decided bring it down re-test at the shack to figure out what was going on.
In the mean time the skimmer was on, the crossband was on both with excellent results. We decided to turn the vhf a bit more to Vieux Fort and see how that would work. In hind sight not a good idea our original setting was way better with much better coverage.
Fast forward about two weeks, all of a sudden no more skim spots! Log in remotely to the pc and take a look, turns out that for some reason the radio was off and not seen by the skimmer software, nor the actual sdr gui. This means a climb to be done soon for that and to carry the sdr back there again..
So it was just the power supply tripped, reset and off it went again. So now we will implement a remote controlled power switch, so when a problem arises we can reset the ps also.
The remote SDR is back up there however thanks to FLOW the isp it is impossible to get back to it since they are doing a double nat. So the next step is a static ip to ensure remote access to the sdr.
When the crossand was on in the West and I used my own at my qth also in crossband we had perfect comms island wide easy. So I started looking for another crossband radio to remove the crossband from my shack, the reason being that I run echolink right here. Now to run the crossband I have to turn off echolink, so we needed another location for the crossband #2. I got an Alinco DR635 and set it up to do 145.530 back to the other crossband radio. Lin had a pretty good site up the Morne, however there are a few FM transmitters right there and they were causing de-sensing. We tried all we could to no avail. I spoke to a good friend and he gave me permission to setup the crossband at his place. We prepared a box with all inside, radio and power supply. We have RG8 coax and the antenna is a Diamond x30 and a 6 element yagi for Uhf. So after doing the preps, Cyril, Filita and myself (J69DS) went up to the site and did the install. Turned it on and boom cross island comms without a hitch. By the next day we got some odd key ups, so we went back up and adjusted squelch levels and that made a vast difference.
So now the J6 Portable group can proudly say we have a full HF CW and RTTY skimmer, and Crossband radios allowing us solid comms across the island between 145.530 and 145.630. We also have an SDR receiver up and witht the static ip it is accessible now.
So our next step is to implement the remote controller power switch, also a timer switch to cause an auto reset of the the ps.