220 Mhz

Discussion in 'General Technical Questions and Answers' started by KE5MLF, May 3, 2007.

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  1. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    CD:

    Actually, the 2.7 KHz to 3.1 KHz bandwidth (depending on the particular version that was used) of ACSB was pretty effective and definitely less than the 16 KHz bandwidth of +/- 5 KHz deviation FM (with a maximum modulation frequency of 3000 Hz). Now with the low deviation of 896 MHz trunking the bandwidth on that band is approaching that of ACSB.

    It was possible for ACSB channels to be less than 7.5 KHz away from the FM 15 KHz channel "splits" that were available for highband systems located more than 35 miles away from each other. Basically the two modes don't even "see" each other unless the frequencies are within about 3 KHz of each other and then it is the FM signal that interfers with the ACSB. A "decent" FM receiver is, for all practical purposes, just about imune from any ACSB signal unless the ACSB transmitter is in VERY close proximity to the FM receiver. This is because the limiter circuits in the FM receiver are designed to eliminate AM components of the signal and ACSB is an AM mode.

    I believe that SEA is still in business. However, Aerotron was sold to an "off shore" owner based, if I remember correctly, out of Saudi Arabia. It was moved from the Raleigh, North Carolina, location where it had been for decades to Florida and eventually went "under". During the 1960s into the late 1980s Aerotron had actually been an excellent manufacturer of two-way FM equipment. Both the design and quality of manufacture were excellent. Unfortunately, their prices were right with Motorola and the vast number of customers would rather have the Motorola "name" when paying "top dollar".

    I purchased an Aerotron 450 MHz community repeater in 1980 primarily because of a "special" that they had for "new" dealers. I was able to get the repeater for over $2000 less than a comparable Motorola repeater (at that time the Motorola would have cost between $4500 and $5000). The price of the Aerotron repeater was right at $2000. The quality of the construction was equal to any Motorola and I had owned the Motorola reconditioned equipment center for the south-central United States from 1970 until Motorola went out of that "end" of the business in 1979. Therefore, I was VERY familar with the quality of Motorola equipment.

    The original Aerotron ACSB equipment was very reliable. However, that equipment was crystal controlled. The second generation equipment was synthesized and that equipment failed repeatedly during the May through October period with the heat in Texas. The repair shop in Lake Jackson, Texas, had come up with some modifications that definitely improved the reliability of the synthesized equipment and Aerotron supposedly was paying this person to modify the equipment (under warranty) for TXU. Unfortunately, Aerotron got "way behind" in paying for the warranty work. I ended up giving a large number of mobile units to the repair shop (he had quite a number of ACSB systems in use in the Texas / Louisiana area) when it was decided to go with the 896 MHz trunking system and abandon the ACSB system. Although TXU was not obligated legally to do anything (since Aerotron was responsible for the warranty work) it was obvious that all of the mobile units were going to be "scrapped" and that a gesture of "good will" towards the repair shop would definitely be in the best interest of the company. As such, TXU would have "lost" the same amount of money by abandoning the ACSB system so we gave around 60 units to the repair shop to pay for the work that had been done. The owner of the shop was happy because he got additional mobile units for his systems.

    Glen, K9STH
     
  2. N4CD

    N4CD Ham Member QRZ Page

    It looks like SEA is still in business

    http://www.comtran-radio.com/220_trunking.html

    They show one model of radio available

    The FCC auctioned off most of the band again around 1999..raised 26 million dollars. Lots of licensees so things really split up.

    There were three national licenses and over 800 smaller area licenses. (as if they could repeat the success of the 'little guys' in cellular who cleaned up big time getting bought out).

    What was intended to be all 'two way' channels, the FCC has relaxed requriements and they can be used for paging and data.

    Likely it will be lightly used, and most of the licensees will go bust.....

    I worked at Motorola and GE....if you ever used the 450 solid state Motrac with 28v PS, and the 90 watt 450 Motrac, I did a lot of work on the power supplies. Then on the System 90 options. Moved to GE and designed much of the Mastr II base station stuff. Lots of fun. Moved into celluar in 1990, then PCS. Then retired.

    GE bet on the GE Marc V 800 MHz trunking system and made a lot of bucks. The 220-222 stuff going on at the same time, and they weren't interested. Also, cellular market was just openinig up, so GE was getting interested in the potential cellular business.
     
  3. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    I never used either Motrac version. However, we did recondition a fair number of the 90 watt output 450 MHz units and a few of the 28 volt units. Also reconditioned a few railroad Motracs. The 28 volt units went to the U.S. Navy for use on certain patrol boats in Viet Nam.

    Also, my senior year in college (Georgia Tech) I was hired directly by Motorola to establish the first Motorola owned portable and pager repair facility away from the Schamburg plant. The location was in Forest Park, Georgia (Atlanta suburb on the south side) at the Area 5 office (the office was later moved to the north side of Atlanta). While there I wrote the suplementary repair manual on the Pageboy I pager (the manual that told how to actually troubleshoot and repair the units).

    Glen, K9STH
     
  4. N2RJ

    N2RJ Ham Member QRZ Page

    No, that is not true.
     
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