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Commercial Radio Antennas - Please keep discussion related to professional, commercially used antennas and antenna systems for the two-way radio industry. Topics for the use of these antennas on amateur bands are accepted here.

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  #41 (permalink)  
Old 08-29-2017, 3:24 AM
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First of all, thanks to everyone else who joined in! Great discussion so far!


Quote:
Originally Posted by RFI-EMI-GUY View Post
alcahuete Do your DTR's have FCC ID AZ489FT5852?
I don't have the radios here with me right now, but I will check in the morning. They are out in the car. One was manufactured in 2016. All the others were manufactured in 2017. They are the brand new models.


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Originally Posted by RFI-EMI-GUY View Post
Does the antenna connector look like what is in this page?

https://fccid.io/AZ489FT5852/Externa...-PHOTOS-611172
That is exactly it. Model is Motorla 8505241U04


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Originally Posted by RFI-EMI-GUY View Post
Can you tell us where you got your mating connector? Model type, Photo? Can you be absolutely sure it fully mates?
The mating connector is factory installed by TESSCO on the coax. No adapters or anything are in play. It is a SMA Female if I recall, same exact as the antenna connector on the 1/2 wave. Pretty sure it's mating. Everything is tight and secure.


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Originally Posted by RFI-EMI-GUY View Post
Also, I assume you don't have any PL259 connectors or adapters? Type N? BNC? all SMA? How are you hooked up?
I ran out of mounts with SMA connectors, so I did use a PL259 pigtail to SMA on one of the mounts I tested. Range did not vary at all. Went quite literally to the exact same block as the others. One mount I used had RG58. The others are both LMR200. No difference in any of the 3.

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Originally Posted by RFI-EMI-GUY View Post
One more question, do you have any sort of 1 GHz power meter and load?
I don't unfortunately. They all stop in the 500-600 Mhz range.

Quote:
Originally Posted by Chickenhawk56
I know little about electronics but quite frankly, can not see why Motorola would purposely degrade the performance of any external antennas except their own. I am with n1das, who feels that it may simply because at those high frequencies, the stock antennas are so close to perfect that anything else with cable lengths and connectors just degrades the signal. Plus, the penetration ability of the 900MHz radios into the inside of a car is so superior that there is little need for an external antenna anyway. My informal tests have easily borne this out.
And that very well could be the case. I'm not ruling that out at all. The only reason they might degrade the performance is so people cannot use external antennas on the radios. I'm not familiar enough with the ISM regs. to know, but does ISM allow for external antennas? It obviously allows for removable antennas, so I don't see why it wouldn't, unless there is a ERP limit there, like in some other services.

I agree that the penetration into the car is definitely quite good. That said, I'm still hitting deadspots, where I have to stick my radio out of my sunroof to keep reception.

I'll be honest, I've probably set some sort of crazy record with these darn things. 14 miles coverage in basically 360 degrees without going up a mountain, is probably pretty dog gone good for a 1W 900 Mhz radio. That said, it was worth the $ to attempt to get rid of the dead spots and extend the range even further. I would really like to extend the coverage to the entire valley out here.
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Old 08-29-2017, 4:56 AM
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Does your SMA connector on the coax have a recessed pin? The reason I ask is I know on my XTS series in 800 MHz go OOR when I use anything but a flat SMA connector antenna. If I use an 800 antenna for my EFJ it doesn't work because the pin is recessed slightly.


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Old 08-29-2017, 8:45 AM
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Your 600 MHZ meter may give you some useful relative forward and reflected power measurements. Places should not be used at all at this frequency. Odd that you saw no effect, maybe some larger loss in effect.

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Old 08-30-2017, 4:55 PM
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Quote:
Originally Posted by evfd1625 View Post
Does your SMA connector on the coax have a recessed pin? The reason I ask is I know on my XTS series in 800 MHz go OOR when I use anything but a flat SMA connector antenna. If I use an 800 antenna for my EFJ it doesn't work because the pin is recessed slightly.


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I think the pin is fine, best I can tell. If not, it would be happening on 3 separate mounts.
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Old 08-30-2017, 6:15 PM
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To accurately measure RF power output from a DTR radio, you are going to need something that can deal with the pulsed nature of a DTR's signal.
EMPower Pulse RF, Burst Power Meter Model 7002-003, 7002-005 All Information| ETS-Lindgren

You'll need around 30 to 40 dB of attenuation ahead of the power sensor to protect it from damage and put the raw level into the sensor at around 0 dBm. The input range is -55 dBm to +10 dBm. From past experience with these sensors it's best to operate around -10 dBm to 0 dBm into the sensor. The final corrected reading will be the raw level into the sensor plus the amount of attenuation you put in between the radio and the sensor. The measurement software supplied with the sensor can automatically correct for the amount of attenuation you put between the power sensor and the DTR radio.

The final (corrected) reading from a DTR radio should be around +29.5 dBm (890 mW).

Good luck.
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Old 08-30-2017, 6:25 PM
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Quote:
Originally Posted by n1das View Post
To accurately measure RF power output from a DTR radio, you are going to need something that can deal with the pulsed nature of a DTR's signal.
EMPower™ Pulse RF, Burst Power Meter Model 7002-003, 7002-005 All Information| ETS-Lindgren

You'll need around 30 to 40 dB of attenuation ahead of the power sensor to protect it from damage and put the raw level into the sensor at around 0 dBm. The input range is -55 dBm to +10 dBm. From past experience with these sensors it's best to operate around -10 dBm to 0 dBm into the sensor. The final corrected reading will be the raw level into the sensor plus the amount of attenuation you put in between the radio and the sensor. The measurement software supplied with the sensor can automatically correct for the amount of attenuation you put between the power sensor and the DTR radio.

The final (corrected) reading from a DTR radio should be around +29.5 dBm (890 mW).

Good luck.
Another method you can use is a calibrated spectrum analyzer and following the FCC's measurement procedures for devices operating under FCC 15.247.
https://apps.fcc.gov/oetcf/kdb/forms...tch=P&id=21124
Details are in the attachment. You will need to have 30 to 40 dB of attenuation between the spectrum analyzer and DTR radio to protect the analyzer's front end.
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Old 08-31-2017, 11:55 AM
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For that matter, you can simply open up the back of a Bird 43 and put a storage scope across the meter movement . Calibrate with a 1 watt CW signal.

I was suggesting simply trying to determine if any signal is getting past the SMA connector.

A field strength meter might suffice as well. It would rule out a 20 dB disconnection.

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Old 08-31-2017, 11:59 AM
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Quote:
Originally Posted by RFI-EMI-GUY View Post
Your 600 MHZ meter may give you some useful relative forward and reflected power measurements. Places should not be used at all at this frequency. Odd that you saw no effect, maybe some larger loss in effect.

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PLACES = PL259'S. DAMN YOU AUTOCOLLECT.

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Old 08-31-2017, 2:44 PM
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Quote:
Originally Posted by RFI-EMI-GUY View Post
PLACES = PL259'S. DAMN YOU AUTOCOLLECT.

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I hate auto-correct.
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Old 09-01-2017, 12:47 AM
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Gen 1 DTRs have been coming back from Depot with Gen 2 guts and antennas. Cheapest upgrade ever for a broken DTR. Send it to the Depot.
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Old 09-01-2017, 12:57 AM
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Quote:
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Gen 1 DTRs have been coming back from Depot with Gen 2 guts and antennas. Cheapest upgrade ever for a broken DTR. Send it to the Depot.
What? What does this have to do with this thread?
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Old 09-01-2017, 1:08 AM
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What? What does this have to do with this thread?
Post #40, son.
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Old 09-01-2017, 1:18 AM
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Post #40, son.
So we've gone from figuring out why external antennas are not working, to sending the radios in to Motorola for a Gen 2 update, son?
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Old 09-01-2017, 1:20 AM
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I don't argue with Kalifornians. You are now ignored.
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Old 09-15-2017, 6:11 PM
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The repair notes from /\/\ for the DTR620 (Latin America version of a DTR650?) show how to disassemble a DTR radio. One of the steps involves removing the top part of the case with the antenna connector. One of the pics in the document shows the connector has a short piece of coax that plugs onto an RF connector on the radio board. I recall there's only one RF connector on the radio board and it's the same connector used by the test fixture.

I seriously think there is nothing special about the antenna connector. The RF power measurement for FCC certification is a measure of the RF power the transmitter actually delivers to the antenna system. Measuring output power at the radio board connector and using the test fixture is most convenient since these tests take time to do at the lab and the radio must transmit continuously during testing. Some transmitter tests such as frequency stability over temperature take hours to do in a thermal chamber. Output power is also measured while in the thermal chamber. The test fixture provides power to the radio so people don't have to keep swapping batteries during testing.

If you measure output power at the antenna connector instead of at the radio board connector, you should get around +29.5 dBm, minus a tenth of a dB or two of cable loss between the radio board and the antenna connector.
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Old 09-15-2017, 7:41 PM
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Quote:
Originally Posted by n1das View Post
The repair notes from /\/\ for the DTR620 (Latin America version of a DTR650?) show how to disassemble a DTR radio. One of the steps involves removing the top part of the case with the antenna connector. One of the pics in the document shows the connector has a short piece of coax that plugs onto an RF connector on the radio board. I recall there's only one RF connector on the radio board and it's the same connector used by the test fixture.

I seriously think there is nothing special about the antenna connector. The RF power measurement for FCC certification is a measure of the RF power the transmitter actually delivers to the antenna system. Measuring output power at the radio board connector and using the test fixture is most convenient since these tests take time to do at the lab and the radio must transmit continuously during testing. Some transmitter tests such as frequency stability over temperature take hours to do in a thermal chamber. Output power is also measured while in the thermal chamber. The test fixture provides power to the radio so people don't have to keep swapping batteries during testing.

If you measure output power at the antenna connector instead of at the radio board connector, you should get around +29.5 dBm, minus a tenth of a dB or two of cable loss between the radio board and the antenna connector.
I think we are full circle back to whether the OP is using a connector that properly mates with the antenna connector.

Also making up cable loss with antenna gain does not net the same performance that would be attained without a cable. Still the OP and others have reported very mediocre results with a variety of external antenna trials.


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Old 09-21-2017, 7:18 PM
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Quote:
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I think we are full circle back to whether the OP is using a connector that properly mates with the antenna connector.
Best I can tell, yes. Seems to fit fine. Have used that connector/mount on other bands/antennas without difficulty. Also tried a couple other mounts and get similar results (to the block, as far as range is concerned).
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Old 09-21-2017, 7:36 PM
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can you use that adapter and then attach the stock antenna using that adapter and another to the radio and see how the range works out with minimum cable loss?
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Old 09-21-2017, 9:40 PM
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can you use that adapter and then attach the stock antenna using that adapter and another to the radio and see how the range works out with minimum cable loss?
Don't know that I have enough adapters to go back to the stock antenna. I'll see what I can come up with though.
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Old 10-07-2017, 3:52 AM
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Had the day off and some extra time today, so decided to do some more testing.

Started by making sure the connectors paired well, and they appeared to. Everything was tight and secure.

The results, 3 miles yet again on both external antennas. New record for me on the 1/2 waves though. Went out to 24 miles today (extending my previous record by 10 miles), before running out of daylight and gas. There was a nice little dirt road I saw and it looks like I can get another 5-6 miles. Should very easily be able to do that.

I think it's time to send one of these to the ISS and let everybody do some weak signal work to space.
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