Motorola XPR 7550(e) BNC Female Antenna Adapter Connector

[K6ASF]

I couldn't find a Motorola XPR 7550(e) and 7580(e) BNC Female Antenna Adapter (Connector). I waited for someone to create one; so, I can purchase three for my Motorola XPR 7550, 7550e, and 7580; but, no luck...no one created one.

Tired of waiting, I met up with my team; and, we created one; and, I'm really happy; because, I can, now, use my coax car-mounted antenna and my coax Diamond X-50 roof-top antenna with my Motorola XPR 7550 and 7550e hand-held transceivers.



We also created an RF ground for our Motorola XPR 7550(e) and 7580(e) BNC Female Antenna Adapter (Connector). We tested it with our equipment; and, it did not interfere with the Motorola XPR 75xx RF specifications; and, our test results were corroborated by the Motorola XPR testing procedures with the AeroFlex testing and tuning equipment by a Motorola technician. The test was done before and after the antenna connector.



I've been using my Motorola XPR 7550(e) and 7580(e) BNC Female Antenna Adapter (Connector) for over two months after we designed and created it; and, it has been performing great!



I really like the fact that I can finally use my Motorola XPR 7550, 7550e, and 7580 with my coax car-mounted antenna whenever I drive around.

Check 6!
/s/ Alfonso Faustino (K6ASF)

 

[kayn1n32008]

The ‘bolt’ connector is live. It’s a ****ty design that does not lend using an adaptor very effective.

In my testing with a DMR repeater running 10w at my house there is a ~25dBm signal strength loss between having a stock antenna attached and having no antenna at all. A friend modified his and my XPR-7550 with a SMA male chassis with a 1.5” coax lead, and removed the bolt chassis plug.
My XPR-7550 now has ~75dBm loss of signal strength between having an antenna attached and no antenna at all.

Motorola made a huge error by using the inferior antenna connection system they designed for the XPR-7550. Its absolute junk.

 

[K6ASF]

In my testing with a DMR repeater running 10w at my house there is a ~25dBm signal strength loss between having a stock antenna attached and having no antenna at all. A friend modified his and my XPR-7550 with a SMA male chassis with a 1.5” coax lead, and removed the bolt chassis plug.
My XPR-7550 now has ~75dBm loss of signal strength between having an antenna attached and no antenna at all.

Motorola made a huge error by using the inferior antenna connection system they designed for the XPR-7550. Its absolute junk.

Hi, kayn1n32008. Thanks for your post.

We thought about doing your type of modification; but, my goal was:
1) not to alter the engineering design of the Motorola XPR 75xx;
2) to make sure I can still bring my transceiver in for servicing at Motorola or its distributors;
3) to protect my warranty -- meaning, not to VOID my transceiver's warranty; and,
4) to use my Motorola OEM rubber-duck antennas if I wanted to, which I do whenever I don't need far distances to hit a repeater;

hence, we created my existing Motorola XPR 7550(e) 7558(e) BNC Antenna Adapter (Connector) in this thread:
- it matches the existing polarity of the Motorola XPR 7550(e) and 7580(e), and
- it has an RF ground for use with coax antennas, such as, but not limited to, car-mounted and roof-top antennas.
- it's non intrusive and can be quickly removed without any scarring to the body nor internal components of the transceiver.

Here are some RSSI numbers from my Motorola XPR 7550e transceiver's on-board instrument system under normal day-to-day use, using my Motorola XPR 7550e BNC Antenna Adapter (Connector).

In this picture, I'm hooked up to my roof-top Diamond X-50 antenna, and I'm communicating with an operator that is ~ 45 ground miles north of my base location.



In the picture, below, I'm using the Diamond SRH 320A; and, I'm hitting a repeater that is ~3 ground miles from my base location.



In this picture, below, I'm hooked up to my roof-top Diamond X-50 roof-top antenna, and I'm hitting a repeater that is ~ 65-75 ground miles north ease of my base location.



Yes, it is unfortunate that Motorola moved away from the XPR 6550 SMA male-type antenna design to the non SMS male-type antenna design in the XPR 75xx.

In my opinion, Motorola did it to prevent users from using coax-type antennas, such as car-mounted antennas, driving sales for their car mobile units like the XPR 5550 -- just my thought, which hasn't been substantiated nor corroborated by Motorola or its distributors.

@kayn1n32008: would you please post some pics of your modification? I have an idea or the way your modification works and looks, because we actually put that type of modification from brain, to pen, and to paper; but, like I mentioned earlier, we deviated from that design to the present Motorola XPR 7550e BNC Antenna Adapter Connector design that I'm am using now.

Thanks.

Check 6!
/s/ Alfonso Faustino (K6ASF)

 

[kayn1n32008]

I can post some photos of my radio when I get home. My friend that did the modification posted a complete write up on another radio site.

 

[kayn1n32008]

How do you provide a proper chassis ground and a 50ohm match to the BNC connector?