Monday, 9 November 2015

Electret microphone project, 6m Sporadic E opening and 2m aurora

Some time ago I bought an electret microphone insert for the Yaesu MD-100 desk microphone. This was sold by W2ENY, who was offering them on eBay for a tiny sum. It arrived successfully, but the plan to install it got delayed behind various "more important" projects.

Pending some parts arriving for other projects, this one reached the top of the pile. It is not difficult to fit, you just have to be careful that your new insert does not move in the fitting and make a noise, or the leads do not have dry joints etc.

W2ENY gives an instruction sheet which takes a bit of figuring out. The mic base seems to have very complex wiring (for a lot of rather unnecessary switches). Basically you change over the inserts and use a dropper resistor to provide low voltage to one side of the new insert. Electrets need to be polarised.
Here we see the mike body, the top section removed on the left and the old insert on the right. I have just wired in the new, much smaller and lighter, insert. I fixed it into the mic body using double sided tape.

The alteration to the base allows the insert to receive a small voltage. I must put a label underneath it reminding me not to use the mic without the base. You could connect it directly and use it as a hand mic, or at least you could before I did this change. Now it will just convey silence if it is not connected via the base.

Electret mics are generally better than the dynamic ones (fitted by Yaesu in this case). Not only is the characteristic tone range closer to the sort of audio we want for DX, they are usually clearer and have higher output.

Initial results seem positive. Doug, GM6ZFI found it better than the supplied Yaesu handmic (which also has a dynamic insert). I can even see that the meters kick up a lot better with the new insert. I may even need to back off the mic gain. The ALC is reaching, but not passing, the end of it's "happy zone".

As luck would have it, the Sun fired out an X-Ray burst today, so I got a chance to try the new mic out on 6m. Well, as it is connected to the FT-450, that is the only band it is used for at present. As usual I was alerted by a burst of Sporadic E on 10m, showing up on WSPRnet as a band of spots from Europeans. What do I do when a band opens ???? - yes, I got to the next band up and try harder there.

The energetic burst triggered off some Sporadic E on 6m. At around 14:00 on SSB I worked IU1FRV, F1RHS, I0KIB and IK5YJY is quick succession. Then I turned on WSPR and heard IK1WVQ.
Those other stations are missing it entirely. Actually, WSPR is not so good for Sporadic E on 6m - as you can see no stations in Spain, Portugal, France and half a hundred other countries, which gives a very poor coverage.

Next stop was 2 metres where I hoped for an aurora. This duly came - at about 16:00. No contacts though, as my key stayed out of use. I heard several GMs working SMs, LAs, OHs and OZs, but it was all too fast for me. I think I heard the Faeroes beacon briefly on 4m, but that was it there.

During the aurora the 10m Sporadic E faded out. No doubt most of HF faded too. Now at 17:20 the 10m Es is back and the aurora has faded out. So I am going to leave it there and see if anything happens later.

I would guess that the X-rays came from a solar flare which might or might not send us some material over the next 36 hours or so. That might mean more fade outs and auroras ... or not as the case may be ...

73

Jim
GM4FVM

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