RadioReference on Facebook   RadioReference on Twitter   RadioReference Blog
 

Go Back   The RadioReference.com Forums > Commercial, Professional Radio and Personal Radio > Commercial Radio Antennas


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.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1 (permalink)  
Old 08-14-2017, 6:21 PM
RFI-EMI-GUY's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Dec 2013
Posts: 2,273
Default end fed 1/2 wave UHF antenna for SABER with MX mount

I would like to make an end fed 1/2 wave UHF antenna for a SABER radio having MX thread mount I am trying to determine how best to match the antenna to the radio, The MX mount does not provide a ground return nor does the radio provide a reliable point to furnish a ground return. The radio chassis of course would be the counterpoise, in any event. The issue is feed point impedance at the stud mount.

I see a lot of discussion about end fed HF antennas, and these always seem to involve a matching transformer or other solution requiring a ground return lead.

I prefer the 1/2 wave as the pattern is cleaner than a 5/8 wave solution.

Has anyone a solution for this?

Oh yes, I have searched for one ready made, but not finding it. Would buy if I can.

(Moved thread to here)
__________________
"Have Spectrum Analyzer, - Will travel" "Going Green"

Last edited by RFI-EMI-GUY; 08-14-2017 at 6:51 PM.. Reason: OP moved thread
Reply With Quote
Sponsored links
  #2 (permalink)  
Old 08-15-2017, 12:27 AM
RFI-EMI-GUY's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Dec 2013
Posts: 2,273
Default

Quote:
Originally Posted by RFI-EMI-GUY View Post
I would like to make an end fed 1/2 wave UHF antenna for a SABER radio having MX thread mount I am trying to determine how best to match the antenna to the radio, The MX mount does not provide a ground return nor does the radio provide a reliable point to furnish a ground return. The radio chassis of course would be the counterpoise, in any event. The issue is feed point impedance at the stud mount.

I see a lot of discussion about end fed HF antennas, and these always seem to involve a matching transformer or other solution requiring a ground return lead.

I prefer the 1/2 wave as the pattern is cleaner than a 5/8 wave solution.

Has anyone a solution for this?

Oh yes, I have searched for one ready made, but not finding it. Would buy if I can.

(Moved thread to here)
Hmm, I might go 5/8 wave if I must?

Any thoughts either way?

Sent from my SM-T350 using Tapatalk
__________________
"Have Spectrum Analyzer, - Will travel" "Going Green"
Reply With Quote
  #3 (permalink)  
Old 08-15-2017, 7:11 AM
MCore25's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jun 2013
Location: Lone Star Republic
Posts: 3,043
Default

This is an interesting idea. Traditionally, Motorola's antennas are purpose built to 37 Ω and due to some experiments they performed back in the late 1960's early 1970's have generally had no design alternative that worked as well in a portable environment as said 37 Ω match.

The saber is still considered one of the best performing portable radios Motorola ever manufactured. It almost makes me wonder if their antenna is a slightly modified end-fed design.


Sent from my iPhone using Tapatalk
__________________
If a repeater IDs and no one is on frequency to hear it, does it even make a sound? Yes, because KC5MVZ is monitoring you
Reply With Quote
  #4 (permalink)  
Old 08-15-2017, 10:13 AM
RFI-EMI-GUY's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Dec 2013
Posts: 2,273
Default

Quote:
Originally Posted by MCore25 View Post
This is an interesting idea. Traditionally, Motorola's antennas are purpose built to 37 Ω and due to some experiments they performed back in the late 1960's early 1970's have generally had no design alternative that worked as well in a portable environment as said 37 Ω match.

The saber is still considered one of the best performing portable radios Motorola ever manufactured. It almost makes me wonder if their antenna is a slightly modified end-fed design.


Sent from my iPhone using Tapatalk
That's good to know about the 37 ohm. The HT220 series required a special matching network jig to test the radio back at 50 ohms. Wish I had known they carried that forward, I would have held onto those jigs. The later model radios all had some sort of 50 ohm port for PSM or testing.

I have this Comet BNC-24 that is a "dual band" antenna, 1/4 wave at 2 meters and 5/8 at 70cm. It gets mixed reviews. I might cobble an MX 1/4 - 24 mount on it and trim it back for GMRS to see how it goes.

The trick is, how to test the impedance. I wish I had a 12M spec for testing Saber/MX type antennas. A long time ago, I got into a discussion with the vendor of the Helical antennas because NPD had substituted -K25 antennas for the original -K08 antennas. The -K08 being NLA.

In the GMRS band, the new antenna had awful field strength and field sensitivity compared side by side with the -K08. The vendor assured me that they were tested and tuned per Motorola specs at "408 MHz", I didn't want to argue with him but thought it odd that a supposed 450-470 MHZ antenna would be tuned at 408 MHZ. I did some more testing later and found that they actually performed better in the Ham band. Also some references claim they were now 440 to 470 MHZ antennas. I never did find an answer. Mostly I am using the 1/4 wave whips now.

I agree about the Saber. I am refurbishing some Systems Sabers right now for Part 97 and for GMRS use as they are certified for Part 95. Since these were all born range 1 govt band, I am plugging in range 2 RF modules from analog donors. I have my test bench set up to do all the required tuning including the deviation balance. I have done 2 so far, and in double checking, it seems they are correct. Got 1 more to do today. Next week I start 6 more.

It is sort of an odd obsession to keep these going, but now with Lithium Ion batteries they are lighter and run forever. Also the batteries don't self discharge.



Sent from my SM-T350 using Tapatalk
__________________
"Have Spectrum Analyzer, - Will travel" "Going Green"
Reply With Quote
  #5 (permalink)  
Old 08-15-2017, 10:57 AM
MCore25's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jun 2013
Location: Lone Star Republic
Posts: 3,043
Default

Quote:
Originally Posted by RFI-EMI-GUY View Post
It is sort of an odd obsession to keep these going, but now with Lithium Ion batteries they are lighter and run forever. Also the batteries don't self discharge.



Sent from my SM-T350 using Tapatalk
I've got several Astro's wearing the lithiums that I use for ranch radios...yea really nice in that aspect. I just wish the AVA was tri-chem.
__________________
If a repeater IDs and no one is on frequency to hear it, does it even make a sound? Yes, because KC5MVZ is monitoring you
Reply With Quote
Sponsored links
  #6 (permalink)  
Old 08-15-2017, 11:16 AM
RFI-EMI-GUY's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Dec 2013
Posts: 2,273
Default

Quote:
Originally Posted by MCore25 View Post
I've got several Astro's wearing the lithiums that I use for ranch radios...yea really nice in that aspect. I just wish the AVA was tri-chem.
The lithium ions that I am using, I repacked with Tenergy 31003 8.4V 2200 MAh protected cells. Opening the Motorola packs is a big chore. The charger I made from a Saber pocket charger housing fitted with a Microchip MCP73213 evaluation board. It charges in a few hours and the light indicates when actually charging.

The trick is that I used the original charging pins, but had to eliminate the protection diode forward drop, so I used a reed switch inside the pack and a magnet on the charging pocket to sense when the battery was to be charged. It works pretty well. I might try a shottkey diode on the next one. I suppose the commercial batteries have a MosFet switch or some sort of fancy arrangement.

I haven't tried the Cut Rate batteries yet. My reason for the repack experiment is that Saber battery support won't be around forever. But cutting open those battery packs with a Dremel tool is a PITA. I need to find someone with a small CNC router.

You could rework the AVA with the MCP73213 or similar and ditch the NIMH's entirely. I am not going back to NIMH.

I am going to buy a couple of the Chinese Li-Ions and try them out while they are still available. Those use a coaxial plug and dedicated charger.
Attached Images
File Type: pdf 51849a.pdf (268.0 KB, 65 views)
File Type: pdf 31003_spec sheet A3.pdf (432.8 KB, 69 views)
__________________
"Have Spectrum Analyzer, - Will travel" "Going Green"
Reply With Quote
  #7 (permalink)  
Old 08-15-2017, 12:20 PM
mancow's Avatar
Member
  RadioReference Database Admininstrator
Database Admin
 
Join Date: Feb 2003
Location: N.E. Kansas
Posts: 6,274
Default

Quote:
Originally Posted by MCore25 View Post
This is an interesting idea. Traditionally, Motorola's antennas are purpose built to 37 Ω and due to some experiments they performed back in the late 1960's early 1970's have generally had no design alternative that worked as well in a portable environment as said 37 Ω match.

The saber is still considered one of the best performing portable radios Motorola ever manufactured. It almost makes me wonder if their antenna is a slightly modified end-fed design.


Sent from my iPhone using Tapatalk
Bendix Kings are the same.
Reply With Quote
  #8 (permalink)  
Old 08-15-2017, 1:21 PM
MCore25's Avatar
Member
  Amateur Radio Operator
Amateur Radio
 
Join Date: Jun 2013
Location: Lone Star Republic
Posts: 3,043
Default

Quote:
Originally Posted by RFI-EMI-GUY View Post
The lithium ions that I am using, I repacked with Tenergy 31003 8.4V 2200 MAh protected cells. Opening the Motorola packs is a big chore. The charger I made from a Saber pocket charger housing fitted with a Microchip MCP73213 evaluation board. It charges in a few hours and the light indicates when actually charging.

The trick is that I used the original charging pins, but had to eliminate the protection diode forward drop, so I used a reed switch inside the pack and a magnet on the charging pocket to sense when the battery was to be charged. It works pretty well. I might try a shottkey diode on the next one. I suppose the commercial batteries have a MosFet switch or some sort of fancy arrangement.

I haven't tried the Cut Rate batteries yet. My reason for the repack experiment is that Saber battery support won't be around forever. But cutting open those battery packs with a Dremel tool is a PITA. I need to find someone with a small CNC router.

You could rework the AVA with the MCP73213 or similar and ditch the NIMH's entirely. I am not going back to NIMH.

I am going to buy a couple of the Chinese Li-Ions and try them out while they are still available. Those use a coaxial plug and dedicated charger.
I've been using Power Products for mine. I've found the Impres chargers for the XTS portables work pretty well with charging the Power Products batteries.
__________________
If a repeater IDs and no one is on frequency to hear it, does it even make a sound? Yes, because KC5MVZ is monitoring you
Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 8:27 PM.


Powered by vBulletin® Version 3.8.2
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
All information here is Copyright 2012 by RadioReference.com LLC and Lindsay C. Blanton III.Ad Management by RedTyger
Copyright 2015 by RadioReference.com LLC Privacy Policy  |  Terms and Conditions