From owner-icom@ns1.qsl.net Sun Aug 24 15:21:03 1997 Received: from ns1.qsl.net (majordom@qsl.net [207.221.20.81]) by oucsace.cs.ohiou.edu (8.8.5/8.8.5) with ESMTP id PAA12940 for ; Sun, 24 Aug 1997 15:21:02 -0400 (EDT) Received: (from majordom@localhost) by ns1.qsl.net (8.7.6/8.7.3) id JAA21755 for icom-outgoing; Sun, 24 Aug 1997 09:48:44 -0400 X-Authentication-Warning: ns1.qsl.net: majordom set sender to owner-icom@qsl.net using -f Received: from neuman.interaccess.com (neuman.interaccess.com [207.70.126.130]) by ns1.qsl.net (8.7.6/8.7.3) with ESMTP id JAA21751 for ; Sun, 24 Aug 1997 09:48:42 -0400 Received: from d120.nb.interaccess.com (d120.nb.interaccess.com [199.88.137.120]) by neuman.interaccess.com (8.8.5/8.7.5) with SMTP id JAA23087 for ; Sun, 24 Aug 1997 09:43:02 -0500 (CDT) Message-Id: <199708241443.JAA23087@neuman.interaccess.com> X-Sender: wiley@pop.interaccess.com X-Mailer: Windows Eudora Version 1.4.4 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Sun, 24 Aug 1997 09:46:04 -0500 To: icom@qsl.net From: wiley@interaccess.com (William Gode) Subject: Re: [Icom] Microphones for IC735? Sender: owner-icom@qsl.net Precedence: bulk X-Questions: k7on@qsl.net >or< http://www.qsl.net/k7on Status: RO The IC-735 is quite a good radio, but lacks in transmit audio quality. The stock hand mike further degrades transmitted audio, but little can be done with other microphones to improve things - at least when plugged into the front panel mike jack. The Heils just don't have enough gain to work with most Icoms. I have a Heil HM-10 and it won't work with my IC-735 - even with mike and vox gain controls fully advanced. The speech amp (and especially the audio compressor) limit the transmit audio quality. I have tried the SM-8, but it seems to pick up too much background noise. I have used Shure mikes, dynamics, equalizers, you name it - without very good results. Recently, I was tuning around the low end of the 40 meter phone band and came across Mo, KC5R, who was transmitting very high quality audio with his IC-735. It turns out that he was running a dynamic mike into an outboard amplifier and feeding the audio signal into Pin 4 of the ACC(1) DIN socket on the back of the rig. This is the normal connection point for AFSK generators on RTTY and other data terminals. Mo had discovered that this point connects the transmit audio through a single transistor (Q63) and then directly to the balanced modulator IC. You need about one volt p-p of audio drive on pin 4, but the results are well worth the effort. There is a PTT pin on that same 5-pin DIN connector, but the VOX circuits are bypassed along with the entire speech amp. I am using a D-104, loaded into one megohm for good low frequencies, which drives a small mike amplifier/compressor connected to the DIN jack, as above. I choke the audio cable with ferrite beads and have no RFI problems back into the audio. After 10 years of crummy audio reports from my friends, my IC-735 finally sounds good! 73, Bill, WA9NHQ >Hello, > I have been using an Icom 735 for about 2 months now, and I really like >it. I purchased the radio with the HM12 handmic, and it seems to work ok. >Audio reports are fine. I am wondering whether it is possible to improve >the audio ---- Submissions: icom@qsl.net From owner-icom@ns1.qsl.net Sun Aug 24 20:43:14 1997 Received: from ns1.qsl.net (majordom@qsl.net [207.221.20.81]) by oucsace.cs.ohiou.edu (8.8.5/8.8.5) with ESMTP id UAA19529 for ; Sun, 24 Aug 1997 20:43:14 -0400 (EDT) Received: (from majordom@localhost) by ns1.qsl.net (8.7.6/8.7.3) id PAA08925 for icom-outgoing; Sun, 24 Aug 1997 15:02:21 -0400 X-Authentication-Warning: ns1.qsl.net: majordom set sender to owner-icom@qsl.net using -f Received: from tir.com (sun.tir.com [205.138.41.6]) by ns1.qsl.net (8.7.6/8.7.3) with ESMTP id PAA08675 for ; Sun, 24 Aug 1997 15:02:07 -0400 Received: from alpha (alpha.shianet.org [205.138.41.9]) by tir.com (8.7.5/8.7) with SMTP id PAA09171; Sun, 24 Aug 1997 15:59:54 -0400 (EDT) Received: from ow47.tir.com by alpha (5.x/SMI-SVR4) id AA19542; Sun, 24 Aug 1997 15:55:44 -0400 Message-Id: <34009330.3FFB@shianet.org> Date: Sun, 24 Aug 1997 16:02:50 -0400 From: Mark and Beth Mowery X-Mailer: Mozilla 3.0 (Win16; I) Mime-Version: 1.0 To: Chris Dorn Cc: icom@qsl.net Subject: Re: [Icom] Microphones for IC735? References: <199708240430.WAA18936@quartz.ucs.ualberta.ca> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: owner-icom@qsl.net Precedence: bulk X-Questions: k7on@qsl.net >or< http://www.qsl.net/k7on Status: RO > Lastly, I have heard that the Heil boomsets don't work very well with some > of the Icom rigs. Apparently they don't have enough output. Is this the case > with the Heils and the 735? Thank you very much for any info. > Chris VE6RDC Chris, Here's some info I got from Heil that you may find helpful. I'll quote the whole thing: "Icom equipment has +5 volts on their microphone audio line to power their CB type "base" microphones. In order to use any of the Heil Key Elements or microphones all Icom radios must have a decoupling cap in series with that audio lead. Mount a .47 mfd cap in the mic connector. To really make an Icom come alive, increase their microphone pre amp feedback resistor by 150K ohm. Easy to do and will certainly increase the talk power of an Icom transmitter ..." FYI, I have an Icom 730 and a 751 and use a Heil boomset with both rigs without the above modification. I do use the the Heil/Icom adapter plug manufactured by Heil. The cap may be incorporated in the adapter, but I confess I haven't looked. I attended a talk given by the man himself near Chicago about a year ago where he stated (you may already know this) that all his mics are purposely designed to be about 10dB down from the "public address" (his term) factory mics to minimize background noise pickup. He recommended speaking very close to the mic and cranking the mic gain ALL the way up, but through on the air tests with a ham friend I have learned that the mic gain on my rigs seems best at about the 3:00 o'clock position, with the boom just about close enough to kiss. Hope that's of some help to you. Good luck and 73, Mark Mowery AA8TC ---- Submissions: icom@qsl.net From owner-icom@ns1.qsl.net Sun Aug 24 22:10:57 1997 Received: from ns1.qsl.net (majordom@qsl.net [207.221.20.81]) by oucsace.cs.ohiou.edu (8.8.5/8.8.5) with ESMTP id WAA21254 for ; Sun, 24 Aug 1997 22:10:56 -0400 (EDT) Received: (from majordom@localhost) by ns1.qsl.net (8.7.6/8.7.3) id RAA17918 for icom-outgoing; Sun, 24 Aug 1997 17:39:05 -0400 X-Authentication-Warning: ns1.qsl.net: majordom set sender to owner-icom@qsl.net using -f Received: from mcfeely.interaccess.com (mcfeely.interaccess.com [207.70.126.131]) by ns1.qsl.net (8.7.6/8.7.3) with ESMTP id RAA17910 for ; Sun, 24 Aug 1997 17:39:02 -0400 Received: from d81.nb.interaccess.com (d81.nb.interaccess.com [199.88.137.81]) by mcfeely.interaccess.com (8.8.5/8.7.5) with SMTP id RAA01302 for ; Sun, 24 Aug 1997 17:36:24 -0500 (CDT) Message-Id: <199708242236.RAA01302@mcfeely.interaccess.com> X-Sender: wiley@pop.interaccess.com X-Mailer: Windows Eudora Version 1.4.4 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Sun, 24 Aug 1997 17:36:26 -0500 To: icom@qsl.net From: wiley@interaccess.com (William Gode) Subject: RE: [Icom] Microphones for IC735? Sender: owner-icom@qsl.net Precedence: bulk X-Questions: k7on@qsl.net >or< http://www.qsl.net/k7on Status: RO Chuck, Yes, a series capacitor is needed on non-Icom mikes, but it is a DC-blocking cap, rather than a decoupling cap. The Icom radios put voltage on the mike line to power their electret mikes. That same voltage can damage a dynamic element, or damage the rig...depending on which craps out first! One microfarad is a good value to use. Heil mikes have a DC blocking cap installed for use with Icoms. My HM-10 has a brand new HC-5 element and is barely adequate with my IC-765, but won't drive the IC-735. The Heil mikes are down about 10 db from most other designs and the Icom rigs just require more drive. I see in the new catalog from Tech America (Tandy) a nifty little mike preamp board for ten bucks which would give one all the needed gain for a Heil mike to work with any Icom. I may give one a try with the HM-10 and IC-765 in the near future. 73, Bill, WA9NHQ >hi bill and group > >i was under the empression that you had to use a decoupling cap with mike's >that were not icom!! the heil will work with decoupling cap or so i am told >by a big contester in the midwest 73 chuck k0gjx > ---- Submissions: icom@qsl.net From owner-icom@ns1.qsl.net Mon Aug 25 00:48:28 1997 Received: from ns1.qsl.net (majordom@qsl.net [207.221.20.81]) by oucsace.cs.ohiou.edu (8.8.5/8.8.5) with ESMTP id AAA24942 for ; Mon, 25 Aug 1997 00:48:27 -0400 (EDT) Received: (from majordom@localhost) by ns1.qsl.net (8.7.6/8.7.3) id RAA18670 for icom-outgoing; Sun, 24 Aug 1997 17:55:05 -0400 X-Authentication-Warning: ns1.qsl.net: majordom set sender to owner-icom@qsl.net using -f Received: from neuman.interaccess.com (neuman.interaccess.com [207.70.126.130]) by ns1.qsl.net (8.7.6/8.7.3) with ESMTP id RAA18665 for ; Sun, 24 Aug 1997 17:55:03 -0400 Received: from d81.nb.interaccess.com (d81.nb.interaccess.com [199.88.137.81]) by neuman.interaccess.com (8.8.5/8.7.5) with SMTP id RAA27232 for ; Sun, 24 Aug 1997 17:49:24 -0500 (CDT) Message-Id: <199708242249.RAA27232@neuman.interaccess.com> X-Sender: wiley@pop.interaccess.com X-Mailer: Windows Eudora Version 1.4.4 Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Sun, 24 Aug 1997 17:52:26 -0500 To: icom@qsl.net From: wiley@interaccess.com (William Gode) Subject: Re: [Icom] Microphones for IC735? Sender: owner-icom@qsl.net Precedence: bulk X-Questions: k7on@qsl.net >or< http://www.qsl.net/k7on Status: RO Chuck, I am using an old RP Electronics RPC-3C stand-alone speech compressor to drive the balanced modulator in my IC-735. The RPC-3C was made in the late '60s to early '70s. It works with high impedance mikes and has enough gain to drive pin 4 of ACC(1) directly. The D-104 crystal element is capable of beautiful low frequency response, but only when looking into a load of more than one megohm. Many tube preamps have at least a 1-meg input impedance, but most solid state amps have much less. Even the built-in preamp on the amplified D-104 has too low an input impedance and swamps out many of the lows. If the preamp/amp has enough gain, simply insert a 1-meg series resistor at the input and the lows will return. This also works with the amplified D-104, which already has way too much gain out-of-the-box. Mo, KC5R was using an ElectroVoice 664 into the aux input of a small 5 watt Radio Shack stereo amplifier. He has *plenty* of available audio drive, plus bass and treble tone controls to adjust. The net effect was very pleasing. Almost any small amplifier would do the job...the requirement for gain being more important that the output power rating of the amp. I guess the bottom line is to experiment and not be afraid to drag out that old junk that's been collecting dust in your attic, or basement. There's also a $10.00 mike preamp board in the Tech America catalog that should do the trick. Have fun, Bill, WA9NHQ > It is my understanding that I will not appreciate as much of an >improvement as I could if I fed this mic as you describe. I am guessing that >you built your own amplifier/compressor, but perhaps you could elaborate on >that. I am assuming that the one volt of audio drive you mention comes from >the amplifier. I am not terribly concerned about losing the VOX circuits. I >am guessing that I could try the Turner 754 through the speech amp by >inserting a capacitor of some kind to block the voltage from the radio. >Perhaps you could comment on how you tried the previous mics through the >speech amp. I am also interested in how you loaded the D104 for lower >frequency response. Forgive all the questions Bill, but I find this >interesting, but haven't really tinkered a lot so this is kind of new. What >was KC5R running as his mic? > >Thanks, >Chris VE6RDC > > > ---- Submissions: icom@qsl.net