The Audio of the first Mk2 Optima’s was pretty crap on SSB with the supplied microphone. We are working on a fix and just started shipping again today Friday 9th March with some mic mods to reduce the lows and bassy response. I will post the fix here and on Yeticomnz web site when we have tested it some more. Bob Nagy AB5N has had a look as well and has fitted one of his inserts with 1uf capacitance in series and says it is working fine. You will find Bob here…..http://www.7000mic.com/ Very interesting read!
The original mic has a 10uf electrolytic cap in series and it looks like this needs to go. I hope he will put this on his website so people with the early model Mk2’s can improve the standard mic. Even if you are using an IC 36 icom mike it can be much improved by Bob. Just tell him it is for the Optima.
PR781, GM4, HM-5 , HM-12We tried some Mics tonight. All the heil mics sounded good. Best of all was the icom IC-36 mic. The JCB 201M with the icom lead also sounded very good and had the advantage that the audio could be tailored somewhat by adding compression. A good combination with the Optima. I also have a mic using a Bob Nagy supplied insert and 0.47 capacitance and that seems to be very good also. Need to test it some more. I was close talking it in earlier tests but once we moved 6′ away I started getting good reports…..
So if you have an optima, any icom compatible Heil mic will work well. The JCB 201 M desk mic works well and the IC36 hand mic is also very good. It is just that the stock mic is not so good. Feel free to buy an insert off Bob and relace the cap! or sent the mic to Bob for a complete overhaul. The good thing is that with the Bob Nagy supplied insert and the FM mod in the radio cranked up full we gained about 1khz in band with. FM is starting to rock. According to Bob it was in the ballpark.
I also wired up a magnum microphone which sounded OK on a radio in the shack but no other tests with it as yet. But it worked! and it has the pot in side which I left in the middle position. The wiring code is as follows to rewire a magnum mic from 257 or S-45 series radio from the six pin magnum plug to the 8 pin icom compatible we use.
Magnum Icom 8 pin Plug
Pin #1 ~ Microphone Audio / White pin 1
Pin #2 ~ Receive / Black pin 6
Pin #3 ~ Transmit / Red pin 5
Pin #4 ~ Down(Up w/22K Ohm Resistor) / Blue Did not connect
Pin #5 ~ Ground / Shield w/yellow sleeve pin 7
Pin #6 ~ +13.8VDC / Brown pin 2