My original question was basically "I guest op at various stations. When I go somewhere with an Icom rig, do I need to add a capacitor to my Heil mic?" The Replies: You need a capacitor to keep the 8 volts off the mic line. I think 1 ufd or large should handle the 600 ohm input impedance. If electrolytic is used, observe polarity - plus to rig end. -Tony, K1KP, fisher@hp-and.an.hp.com Yo Foxxy Scott. You may have a mike connector with cap in it & you don't even know it. If you didn't you wouldn;t get much audio out of the headset. Now on the VB. I use it & its neato-keeno. But, your host's PC must have an SB card. The cap you need is 0.47 uFd. I think thats what Heil is putting in the connectors of the ProSets these days. I use a mic mixer with my setup where I can record, play back to various devices like a stereo, the rig, etc... GL & let me know how you make out... .............................................................................. 73 de Walt Kornienko - K2WK Frankford Radio Club Internet: waltk@pica.army.mil This is a good question. Would appreciate any replies you get. I too usually guest op. I have a specially modified DX-Engineering rig-computer interface so I can use it with Icom, Yaesu, Kenwood, and Ten Tec. I bought a bunch of mike plugs to do what you are thinking, but never got around to making the adaptors. I seem to remember that something like this was being advertised in the latest Heil blip. Ken WM2C ----------------------- Headers ------------------------ From ken.silverman@atlas.ccmail.AirTouch.COM From: eric%modular.UUCP@cs.arizona.edu Subj: Re: Capacitor on Icom mic line? To: KA9FOX Scott, The ICOM radios have mic power on the mic audio pin of the radio connector. This usually amounts to about 8 or 9 volts DC. If you plug a low impedance DC coupled mic into this plug, the result is usually : 1. The mic works unless its power dissipation is high enough to fry the coil. 2. If the mic survives, the current limiting series resistor burns out and the radio will no longer power the ICOM mic properly from the connector. If the owner is also using a low impedance dynamic mic, he probably already burned out the resistor and won't notice any damage that you did. I have seen cases where 2 above happened but the resistor didn't completely burn open. The resistor value got higher but still had enough conductance to marginally power the ICOM mic. You should definitely include a 1 uF tantalum cap in the mic audio line (+towards the radio) when using lowe impedance dynamic mics with the ICOM radios. Actually, only 0.8 uF is required to get response all the way down to 300 Hz. 73, Eric N7CL A 1uf 10-16 volt electrolytic or tantalum cap with positive end towards the mic plug will do. All Icoms have 8v on the mic line to power electret element. 73 Bob Kile, KG7D "rkile@delphi.com" From: pub759@idptv.idbsu.edu Subj: ICOM and Heil Mics To: KA9FOX Hi Scott, This is Jim KK7A in Boise, ID. I ran a Heil with the 765 and did have to block the audio lead with a cap. Without one, if I remember right (I now own a TS-850) it keyed the transmitter just by plugging it in. As far as a value...I think it was a .1mf if I remember right. I did notice that I didn't have much audio for the VOX on the 765. There was enough to drive the transmitter but could have used a bit more for the VOX. Hope this helped. Have fun in FD this weekend. I'll be handing out ID from home as 1D this year. Oh well.... Jim I should also put a capacitor on the mic line? Do I need to do this? If so, what is the value? K1VR: Yeah, put the cap in. Makes no diff to your 930. I'd buy a small cast aluminum box (RF tight) and mount a female eight pin wired for Kenwood. Put cap in box. Then on far side of box mount another 8 pin chassis mount. Now you can simply use a jumper for ICOM or a jumper for Kenwood or a jumper for Yaesu, depending on what they have wherever you land. I use this method because I just swap jumpers when ops show up here. -- Fred Hopengarten K1VR Six Willarch Road * Lincoln, MA 01773-5105 home + office telephone: 617/259-0088 (FAX on demand) internet: k1vr@k1vr.jjm.com Yes, a capacitor is needed! Before I installed one I could still work people but got several comments of "bad audio". As soon I installed the capacitor, all the audio problems went away and the transmit audio became clean. As I recall, the capacitor I used was 2.2 uF electrolytic with the positive side wired to match the polarity of the output voltage. I think the output voltage is positive but I have not looked at this in some time so I'm not 100% sure. 73, Steve Thomas N6ST stevet@hpscit.sc.hp.com