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SeaCall last won the day on January 30

SeaCall had the most liked content!

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About SeaCall

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    Owner of Defender 110 FFR Tithonus, with working display of Clanman Radio equipment.
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    Radio Communications Engineer
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  1. Hello As I understand the rules, persons and businesses can obtain licences from Ofcom to operate or repair radio transmitting equipment under Testing and Development (Radiating) conditions. Also testing under Suppressed Radiation conditions is exempt from licensing between certain frequency limits and levels of radiation. The PRC344 operates between 245-399.99MHz which lies outside the nearest band where suppressed radiation is permitted (244-400MHz).and where the limit for radiated power is 30dB uV/m measured at 30 metres. This would indicate that testing this equipment even on receive without a valid licence may not be permitted. The frequencies and limits allowed for testing radio equipment under suppressed radiation conditions is defined in The Wireless Telegraphy (Testing and Development Under Suppressed Radiation Conditions) (Exemption) Regulations 1989. Statutory Instrument No.1842 . The PRC344 operates on an Military Aeronautical band on which even the reception of signals, without proper authority, could be considered an illegal act. Potential owners of this equipment should be aware of the possible implications for anything other than non-working display. I hope this helps clarify the situation. Barry G8DXU
  2. Hi Folks Just to clear up a question as to the origin of the note entitled " IBMS preventative maintenance/repairs" as quoted by "Landymad" and "Bob042" This was one of the early notes made during early investigations at SeaCall Ltd. into faults found in these units. We had acquired a large quantity of non-working IBMS units which were subsequently repaired in our workshop. This note was sent out as an email to assist one or two people several years ago when there was little good info on these items. It appears to have done the rounds and to have been of some assistance! With complex systems such as the IBMU the fastest way to isolate faults is to swap cards for known good items. But it is acknowledged that amateurs will often not have good spares available. In this case it is suggested that the whole IBMS is initially powered from a current limited laboratory supply set to 24V. Whilst some of the active components have been know to fail the Tantalum Capacitors are the main source of problems. Wholesale replacement of these normally solves most faults. It is worth noting that some failures in the PSU card can result in output voltages being much higher than normal. This will tend to exacerbate damage to Tantalum Capacitors and semiconductors in other boards. Experience has shown that if one only replaces the capacitors found to be faulty, then supplies will often fail in the near future when other capacitors subsequently fail! As noted in my earlier posts I intend to publish some more comprehensive repair information shortly. Barry G8DXU
  3. I have received an email from "Pentecost" regarding the manual that I am preparing on IBMU repairs. This is well underway but has been slowed down by my work on the Clansman PSU50A repair document. Members interested in this and the PRC320 can search the http//sars.club website (The Southdown Amateur Radio Society). The document "Clansman PSU50A repair guide" will probably come up in search engines as will the "Clansman PRC320 RT320 repair and servicing" These abridged articles will give members an overview of common problems and suggestions for suitable repair solutions. The IBMU document should be completed in the near future and will probably be published on the SARS site in the first instance. Barry G8DXU
  4. Hello I have just found this thread on IBMU repairs which is interesting. Having repaired many of these units, most of the comments given above are factual and valid. The main problem with these units is, as noted by Iain, the Tantalum Capacitors failing Short Circuit. Most problems lie in the Power Supply Card although the Analogue modules frequently cause problems. Faulty Tantalum Caps often appear burnt out and these are easy spotted. Otherwise I would advise the use of a short circuit locator, such as the Polar "Tone Ohm" which will save a lot of time. The white PSU modules on the PSU card are fairly resilient but will fail if they see a short circuit for long periods. Spares are difficult to obtain but other commercial PSUs can be substituted by drilling new mounting holes in the PCB. I suggest running the main PSU card from a 24V bench power supply and checking the various voltage outputs. I am currently preparing a document that details basic repairs on the IBMU which will be available shortly. I also have a number of PSU cards that have been serviced and fully tested should this be of interest. My location is in Eastbourne. Barry G8DXU
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