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Tuesday, 30 September 2014

A White Stick?


Been fiddling with a new antenna today; I bought it from "My Favorite Ham Store" LAM Communications. I only ordered it yesterday afternoon, and it duly arrived this morning by FedEx:

LAM Communications

This antenna is a "White Stick" made by Diamond Antennas and is designed to work on 6M (50Mhz), 2M (144MHz) and 70cm (433MHz).

As I have no antenna analyser that will work on 2M or 70cm I have attached the antenna (now it's up in the air) to the Return Loss Bridge we made back here:

and also to a commercial Rigol RLB I have. Both gave almost identical results when using the Spectrum Analyser in SWR mode.

Here's what we see on 50MHz:

You can see a clear resonant point at 51.47MHz with a return loss of 23dB and an SWR of 1:1.15 (ish) - most excellent.

Here's what we see on 144MHz:

An almost identical clear resonant point, this time at 145.04MHz with a return loss of 34.9dB and an SWR of 1:1.03 - again most excellent.

Here's what we see at 433MHz:

Now this shows that the antenna is resonant way wider than the whole of the 70cm band - the measurements at 433.5MHz are 12.8dB return loss which is an SWR of 1:1.5 - again that's perfectly acceptable.

The antenna included a wire radial for 50MHz which I simply attached to the mast and a SWR adjustment which I just stuck in the middle.

Cats didn't help much, too busy waiting for tea:

Good egh?

Local conditions.

Sunday, 28 September 2014

How much RTTY?


This weekend was the CQ WW RTTY Contest - by far the granddaddy of all RTTY contests with wall to wall RTTY signals on the bands.

I've had a dabble, and here is my log as a map:

Fun. egh?

Monday, 22 September 2014

It's a 4 hour sprint!


Last night was the BARTG 75 baud RTTY September sprint contest.

It's only a 4 hour test so even my boredom levels coped well with this one. 75 baud RTTY is quite odd really as I suspect I spend as much time thinking about what just happened as I save by the transmissions being faster. Net result is just more confusion on my part!

Anyhow, I have entered my meagre efforts into the contest, here's my log as a map:

Meanwhile, Chopsy has a new hidey hole:

And Pepper has found a transformer to perch on:

Fun, egh?

Saturday, 20 September 2014

The Continuation of the Transverting Conundrum


I've been fiddling some more with my experimental 4M Transverter project.

I've built the RX converter:

This is fairly simple in that it takes the 70MHz signals from the antenna, amplifies them and then mixes them with the 60MHz local oscillator we developed last time:

and results in a 10MHz signal at the output. I've done some initial tests on this down converter and it seems to work as expected.

The transmit side is still work in progress:

On the right you can see part of a traditional doubly balanced mixer - I've used BAT85 diodes this time for a change.

The mixer mixes the 10MHz drive signal with the 60MHz local oscillator to make the 70MHz (plus all the harmonics and also the difference). This is fed through a band pass filter, which sweeps like this:

and then amplified and passed through another filter. The second filter is also a band pass at the moment, but I expect I will swap it for an identical low pass filter I made for the RX side - the second band pass filter is no way near as good as the first for some reason.

I then need to make a linear amplifier to increase the output to about 10W to drive my linear.

Good, egh?

Monday, 15 September 2014

To Transvert or not to Transvert


Been thinking more about my antics on 2M & 4M Meteor Scatter:

And wondering how my TS-990 would perform with transverters for 2M and 4M.

There are many designs out there for transverters, one of the best I have found are here:

Sam does a transverter for 2M and 4M; I have decided to join his waiting list....

In the meantime, you may recall we had a bash at some 4M kit a while ago, so I thought I would build on that experience and have a go at making a 4M transverter myself:

So here is what we have so far, the "traditional" approach would be to build an oscillator for 42MHz and then mix it with 28MHz IF. Well, I don't have such a crystal so I have started with a 20MHz crystal oscillator and a frequency tripler to give me a LO of 60MHz. This mixed with a 10MHz (30M) IF will get us to 70MHz.

Here's the LO:

It's output looks like this:

and its harmonics like this:

So I need to feed this through a low pass filter, which inits simplest of forms, looks like this:

The one I have made above sweeps like this:

So this is looking like a reasonable start.

I need to make the down converter next, this will be made with some dual gate mosfets - I've ordered some BS981s which should perform well at these frequencies. Hopefully they will drop through the letterbox any day soon.

Cat's not been helping much at all today:

Good egh?