Newsgroups: rec.radio.amateur.misc From: Chuck Adams Subject: IC-901A Frequency Ranges Message-ID: <1992Oct6.135935.26944@sunova.ssc.gov> Sender: usenet@sunova.ssc.gov (News Admin) Nntp-Posting-Host: 143.202.130.11 Organization: Superconducting Super Collider Laboratory Date: Tue, 6 Oct 1992 13:59:35 GMT Lines: 69 In article paul@n3eop.pgh.pa.us (paul) writes: >Does anyone know the extended range of the various IC-901A modules? I'm >particularly interested in the 10m and 6m modules... and how they relate >to the VHF-Lo band. > >Any other undocumented tricks with the '901? Here are the frequency coverage ranges for the various band modules and the modifications to the control head diodes to get these extended ranges: Band Range (MHz) RX diode TX diode 10m 28-40 24 out 21 in 6m 40-54 28 out 26 in 2m 138-174 no change 18 in 220 216-236 no change 12 in 440 400-479 25 out 23 in 1200 1240-1300 no change no change To modify, remove the back of the control head and add or remove diodes from the marked pads as described in the above table. notes: coverages are for RX. TX may not work over entire range, but will come close. RX sensitivity is front-end tuning dependant. 10m, 6m, 2m and 1200 modules will have OK RX sensitivity over most of their range. 220 RX sensivity is unknown over its' range. 440 RX sensitivity will cover about 25 MHz with good sensitivity, tuning out of the box is from about 438-463. The 3 helicals can be retuned to any where in the 400-479 MHz range, but you can still only get the 25 MHz or so spread. If you have severe intermod problems while listening to 440 MHz frequencies, I would recommend retuning the helicals down in frequency to attenuate the strong 450-460 MHz signals from the front end. The intermod will almost completely go away. Of course, the sensitivity above 450 MHz will suffer, but most of the signals you would probably be interested in listening to will probably be quite strong to start with, so you will probably still hear them just fine. If you have access to a tracking generator and spectrum analyser, there is a small two pin jack on the UHF board from which you can monitor the helical response. Connect the tracking generator to the antenna jack and the spectrum analyser to the two pin jack. Other '901A tricks: Memory and microprocessor reset - turn power on while holding down check and memory write buttons. Crossband repeat - turn power on while holding down check and lock buttons. If crossband repeat has been engaged, the "lock" display will flash. PL can not be selected in either band for crossband repeat to work. If you need PL to operate the repeater you are linked to, generate it on the radio you are using to talk to the 901. The PL will pass through the 901 just fine to access the linked system. Since the radio is in the locked mode, you can't change frequencies or bands during crossband repeat. To disengage crossband repeat, turn off power or press lock button. If there is no audio during crossband repeat, open up the front of the dual-band unit by removing the plastic cover behind where the control head would plug in if the 901 is not used in the remote-control head configuration and look for a slide switch mounted on the edge of one of the vertical circuit boards and slide it the other way. The switch does not seem to come in any pre-determined configuration from ICOM, so some radios work OK for crossband repeat right out of the box, and some require the switch to be in the opposite position. I would be very interested in any other mods or tricks for the 901. Chuck Adams, WB5WRR (The Chuckster) Not an official document of DOE, SSCL, URA or EG&G "I cut you three ways, man: quick, deep and frequently" Internet: chuck_adams@qmail.ssc.gov Copied from the QRZ! Windows Ham Radio CDROM