XPR3500 External Antenna Adapter?

BigDogg795 · Jan 22, 2016

So recently I downgraded from an XPR7550 to an XPR3500 because of cost concerns and the perpetually rotating channel selector. While I do have some minor regret over lost features I realized that due to the lack of GPS the antenna port on the 3500 is a standard SMA connector (no center pin contact).

If that's the case; I should be able to hook the 3500 up to an external antenna using an SMA-BNC adaptor, shouldn't I?

Thoughts from the audience?

N4KVE · Jan 22, 2016

No not SMA. It's the same antenna jack that was on your 7550. There is no adapter made yet that screws into the 7550/3500 that's out there. It's sort of similar to the old MX/Saber antenna jack, but different threads. I own 2 3500's, & they are great radios. Lately I've been leaving my 7550 at home, & carry the 3500.

BigDogg795 · Jan 22, 2016

MOONBOOTS said:
No not SMA. It's the same antenna jack that was on your 7550. There is no adapter made yet that screws into the 7550/3500 that's out there. It's sort of similar to the old MX/Saber antenna jack, but different threads. I own 2 3500's, & they are great radios. Lately I've been leaving my 7550 at home, & carry the 3500.

Damn...well hopefully with the popularity of DMR in both the commercial and HAM worlds some enterprising company will create something.

I just figured the lack of center pin would let me do something with the 3500. I really like the 3500...it's well built and seems decent for the price given alternatives like the MD380. The fact the 3500 does the whole band split like the 7550 is a plus also...eliminates the need for a second UHF radio. I just hope Motorola makes a mobile with the full range too.

Sent from my Startac using 1XRTT.

N4KVE · Jan 22, 2016

The 3500 uses the same RF board as the 7550. I recently picked up my 2nd 3500 used on that famous auction site for $200. It looked new, & was still under factory warranty. The stubby antenna works extremely well. I figured with the wide coverage [403-512] the rx would be a little deaf, but it's hotter than any 6550 I ever owned. Enjoy the radio.

Project25_MASTR · Jan 22, 2016

I guess the real question is, why do you want to put a differnt antenna on the radio? Motorola makes an adapter (it'll set you back a few bills) and you could proably hack a PSM to get the RF off of the accessory connetor (similar to what Motorola did with the Saber service cable).

N4KVE · Jan 22, 2016

When the 7550 first came out, I felt bitter that I couldn't just pop an adapter into the connector like I could on my 6550. But I'm lucky that in my county, there are so many DMR repeaters, that it's totally not necessary to use an external antenna. And the cable that M sells for hundreds is only for alignment, as it's connected to the main board. One tug on that cable while it's connected, & serious damage to the radio can occur. GARY

KG4INW · Jan 22, 2016

Unfortunately, there's no RF on the side connector like the first gen TRBOs had so no PSMs work on second generation radios.

Project25_MASTR · Jan 23, 2016

KG4INW said:
Unfortunately, there's no RF on the side connector like the first gen TRBOs had so no PSMs work on second generation radios.

That's unfortunate. I haven't spent a lot of time around 2nd gen TRBO hardware. Most recently I've migrated my attention to Simoco's Xd line.

Sent from my iPhone using Tapatalk

N1GTL · Jan 26, 2016

The XPR7550 does have an external connector. If you remove the battery, you will see the top plastic piece on the back right above it. The piece has XPR7550 printed on it. The plastic piece will slide down and reveal an antenna connector. Motorola sells the connector that connects to it. It is used for connecting the radio to a service monitor for alignment and testing. I don't think it was meant or should be used for an external antenna.

I am not sure if the XPR3500 has the same connector, I have only removed one from the XPR7550

N4KVE · Jan 26, 2016

N1GTL said:
The XPR7550 does have an external connector. If you remove the battery, you will see the top plastic piece on the back right above it. The piece has XPR7550 printed on it. The plastic piece will slide down and reveal an antenna connector. Motorola sells the connector that connects to it. It is used for connecting the radio to a service monitor for alignment and testing. I don't think it was meant or should be used for an external antenna.

I am not sure if the XPR3500 has the same connector, I have only removed one from the XPR7550

Yes, that connector is hundred's of $, & since it's connected directly to the main board, you do not want to use it out in the field. It's for use on the bench only.

BigDogg795 · Jan 30, 2016

MOONBOOTS said:
No not SMA. It's the same antenna jack that was on your 7550. There is no adapter made yet that screws into the 7550/3500 that's out there. It's sort of similar to the old MX/Saber antenna jack, but different threads. I own 2 3500's, & they are great radios. Lately I've been leaving my 7550 at home, & carry the 3500.

MOONBOOTS said:
Yes, that connector is hundred's of $, & since it's connected directly to the main board, you do not want to use it out in the field. It's for use on the bench only.

Sorry, not to be a pain, but genuinely not familiar enough to comprehend something. At the risk of damaging my radio threads, I attempted to ever so gingerly screw in the SMA to BNC adapter I purchased into my 3500 (since it doesn't make sense to return it and I can still use it on my actual SMA portable). It screwed in without issue; my question is this: SMA is supposed to have the center pin; which IIRC the 7550 does in fact have however my 3500 does not. My antennas have a "dimple" but no full allowance to accept a full pin. I'm trying to educate myself on antenna signal leakage and what not; I'm under the impression that the SMA antenna adapter won't work simply because it expects to transmit the signal through the center pin; since my 3500 doesn't have the pin it would basically see the adapter as the antenna instead of the actual external antenna, correct?

Thanks for putting up with me on this lol.

riveter · Jan 30, 2016

The whole new 2nd gen series of XPRs, 7550 included, do not conduct RF via a center pin. If you screw a center-pin conductor antenna into the jack for it, including an adaptor, the jack will conduct the RF via the housing/shielding of the antenna base. If you are connecting a cable, it will conduct the RF into the braided outer cable conductor; if you are connecting an adapter, it will conduct into the frame. The central antenna element that's supposed to carry the RF and resonate to it will only get secondary radiated RF that it receives from the nearby non-connected shielding and jack. Basically, though the antenna ASSEMBLY is connected to the jack... the center conductor is not, so the antenna is actually receiving RF rather than transmitting it (and isn't connected to anything).

BigDogg795 · Jan 30, 2016

dpcain said:
The whole new 2nd gen series of XPRs, 7550 included, do not conduct RF via a center pin. If you screw a center-pin conductor antenna into the jack for it, including an adaptor, the jack will conduct the RF via the housing/shielding of the antenna base. If you are connecting a cable, it will conduct the RF into the braided outer cable conductor; if you are connecting an adapter, it will conduct into the frame. The central antenna element that's supposed to carry the RF and resonate to it will only get secondary radiated RF that it receives from the nearby non-connected shielding and jack.

Ok, gotcha, completely understand the issue now! I appreciate the explanation!

N4KVE · Jan 30, 2016

BigDogg795 said:
SMA is supposed to have the center pin; which IIRC the 7550 does in fact have however my 3500 does not. My antennas have a "dimple" but no full allowance to accept a full pin.

The 7550, & 3500 do not have a pin, & both use the same antenna. Only the "sold in Canada" 7550 IS which is partially blue in color, CSA approved, & is $1500 has a center pin. Do you have that radio? GARY
Read the whole article. http://www.va3xpr.net/motorola-mototrbo-xpr-7550-s-dmr-portable-radio-review/

BigDogg795 · Jan 30, 2016

MOONBOOTS said:
The 7550, & 3500 do not have a pin, & both use the same antenna. Only the "sold in Canada" 7550 IS which is blue in color, CSA approved, & is $1500 has a center pin. Do you have that radio? GARY

No, but I could have sworn my 7550 had a pin. Eh, I never really took the antenna off though and I might have just confused it with the 6550 I use at work.

XPR3500 External Antenna Adapter?

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