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  #21 (permalink)  
Old 06-23-2017, 12:56 AM
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How True! I wonder how many trillion $ to convert CHP to UHF P25?

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Lots.

They've looked at doing 700MHz P25 in urban areas, and they could actually be doing it in some places. I know one of my high sites was being considered for CHP 700MHz, but it didn't work out.

It'd be idiotic for them to even try. They'd never get the coverage they have now.
CalTrans is moving away from low band (they were another huge user) and going to 800MHz. The number of 800MHz conventional sites they've had to install is silly, and they still don't have the same coverage.

City of San Francisco has kept some of their low band gear. Last time I looked in one of their cars, they had an old MaxTrac low band radio in it.
San Francisco water company still uses low band for their stuff. They get a lot of their water supply from the Sierras, so almost 200 miles of pipeline to get it. They rely on low band coverage for their guys working out there, but are looking at UHF for their closer in stuff. Kenwood was bidding on their system, and they saw the only way to do what they want, and keep the price reasonable, was to keep low band for the pipeline stuff and use UHF (I think it was UHF) for the plants and stuff around SF.

I'd still like to get myself a low band pair and set up a repeater on one of my high sights and see what she'd do. Maybe some day I will.
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  #22 (permalink)  
Old 06-27-2017, 12:05 PM
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Just a comment: We have state-wide commercial needs at the lower 30+MHz, plus the non-federal interop channels, plus a system in upper 45s. Two radios in each location as a result unless we $upgrade. So, yes, there is room for new continuous coverage rigs.

On a separate note, I'm waiting for someone to come out with low-band digital trunking ... just to stir the pot. Would sure make more sense than building more and more rural 700MHz towers... Think of the new opportunities What else are they going to do with VHF-Lo that's being vacated?
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Old 06-27-2017, 12:42 PM
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Depending on where you split is, the TK-6110 will do 35 to 50MHz in one model. If you are below 35, then you're stuck.

As for low band digital trunking, that'd be interesting. I'm not sure with skip that it'd work well, too much depends on a clean data stream. Also, the piss-poor performance of low band portables would not work well for many users.
As a mobile and base only system, it's hard to beat.
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Old 06-27-2017, 12:54 PM
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In the late 1970's the Santa Barbara County Sheriff moved from a 45MHz system to a 460MHz system. They naively thought that they could get by with the same sites they had with the low band system. It took years to fix and there are still areas where deputies are equipped with 150MHz fire radios to enable them to reach dispatch. Now the Grand Jury is investigating coverage problems and is recommending a 700MHz system. They never learn.

Also, in the late 1970's I worked with the Santa Barbara County Fire Department and actually suggested that they could solve some of their coverage problems with their 150MHz system by moving to 33MHz. LA City had vacated the band and large numbers of frequencies were available. The reaction was one of total disbelief. The didn't want to consider "old fashioned" frequencies. They have built out the 150MHz system with multiple linked repeater sites. It works fairly well, but suffers from phase distortion and requires the repeaters to be synched almost daily.

When LA City moved to 800MHz they got a waiver from the FCC not to have a trunked system. Very smart.
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Old 06-27-2017, 1:55 PM
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Originally Posted by kf8yk View Post
Similar form factor, but not the same. At one time the RF Technology Eclipse series was resold/relabeled as the DX Radio Systems Millennium series.


The Eclipse 2 is relabeled by Icom currently. The Eclipse 3 (which isn't fully into production) will also be relabeled by another vendor (not Icom but well known for trunking). The Eclipse 3 is unique in that it is a SDR and will continuously tune from low band through 800 MHz in a single piece of hardware.

Also, the Eclipse 2 that hit CAP a few years ago spec'd out at 5% BER @ -128 dBm. In comparison, the Quantar Motorola sent spec'd at 5% @ -118 dBm.


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Old 06-28-2017, 7:07 PM
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For an HT and they may cost an arm and a leg (maybe first born too), put tactical on it and it usually adds a 0, check out the Codan Sentry.
https://www.codanradio.com/product/sentry-v/
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Old 06-29-2017, 1:32 PM
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Default TAIT our of Australia might still have some

I believe TAIT radio out of Australia is still making quality lowband radios. A quick check of their website shows no...but last time I called them they still had some.
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Old 06-30-2017, 8:41 AM
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I would convert a TK-690H to be a base station, certainly sounds like the most cost effective route.
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  #29 (permalink)  
Old 06-30-2017, 9:02 AM
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Originally Posted by bc780l View Post
Just a comment: We have state-wide commercial needs at the lower 30+MHz, plus the non-federal interop channels, plus a system in upper 45s. Two radios in each location as a result unless we $upgrade. So, yes, there is room for new continuous coverage rigs.
Even if you find a radio that covers that whole split, what are you going to use for an antenna? I have not found any low band antenna with more than 6 or so MHz of bandwidth, and most antennas are much less than that.

Another reason that I'm in the process of abandoning low band is the high noise floor. Many of our sites still work fine, but many are quite deaf. There isn't much rhyme or reason to which sites are fine and which aren't. My current theory is that other transmitters with a high duty cycle (trunked systems and paging) are creating PIM on older towers that may need a paint job.

We used low band for decades, but have recently had to install a voted system to get the same coverage we had in decades past.
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Old 06-30-2017, 9:15 AM
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Quote:
Originally Posted by ko6jw_2 View Post
In the late 1970's the Santa Barbara County Sheriff moved from a 45MHz system to a 460MHz system. They naively thought that they could get by with the same sites they had with the low band system. It took years to fix and there are still areas where deputies are equipped with 150MHz fire radios to enable them to reach dispatch. Now the Grand Jury is investigating coverage problems and is recommending a 700MHz system. They never learn.

Also, in the late 1970's I worked with the Santa Barbara County Fire Department and actually suggested that they could solve some of their coverage problems with their 150MHz system by moving to 33MHz. LA City had vacated the band and large numbers of frequencies were available. The reaction was one of total disbelief. The didn't want to consider "old fashioned" frequencies. They have built out the 150MHz system with multiple linked repeater sites. It works fairly well, but suffers from phase distortion and requires the repeaters to be synched almost daily.

When LA City moved to 800MHz they got a waiver from the FCC not to have a trunked system. Very smart.
What else do you expect with the radio vendors pushing all this migration. They are not stupid and know that many more sites will be needed to produce the same coverage as any low band system they have now. But you can't make any money if you don't force your customers to upgrade.

This is not a new thing. Been going on since the early 70's. Only now they are pushing a trunking system so the users have to buy more expensive radios. The radio vendors are smiling all the way to their bank.
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Old 06-30-2017, 9:24 AM
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Another reason that I'm in the process of abandoning low band is the high noise floor. Many of our sites still work fine, but many are quite deaf. There isn't much rhyme or reason to which sites are fine and which aren't. My current theory is that other transmitters with a high duty cycle (trunked systems and paging) are creating PIM on older towers that may need a paint job.

We used low band for decades, but have recently had to install a voted system to get the same coverage we had in decades past.
Painting a tower is not going to resolve noise issues. If it is from the tower itself, you will normally will find that there are loose and rusty brackets that are moving with the wind. Add a little moisture and you now have a diode junction that will drive a receiver crazy.

I think that if you look around the site, you will find that a good portion of you noise floor is from IP devices and non shielded interface IP cables between the boxes. If there is a cable TV feed to the site, they are very prone to leakage and cause a real problem.

last place that can cause a bunch of noise is any computer and display that may be left on at the site will drive you crazy trying to locate where the noise is coming from. Between poorly designed IP network devices and everything that goes with it, low band systems are doomed.

I know of a number of 6 meter ham repeaters that had to be shut down due to the high noise floor killing receiver reception. High noise floor problems is a dreaded fear of any low band user today. To add to the problem, most radio shops don't have a clue how to track it down. Many of them don't even own a spectrum analyzer that can help locate the noise source.
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Old 06-30-2017, 9:39 AM
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Originally Posted by MOTEX View Post
Carnival huckster two way salesmen and bribes aplenty have all but eliminated low band use

At one time the entire county was covered by ONE 39 MHz repeater

Today, it takes 9 tower sites on 800mhz to do the same job!

modern 911 systems have turned into a massive money pit and cesspool of bribes instead of providing reliable communications at the least cost to the taxpayer

Can you give us data on these "bribes" you speak of ? Any links to a newspaper article that validates these bribe claims you keep making on RR ?
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Old 06-30-2017, 10:08 AM
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Noise floor is getting atrocious on low band. Both at the sites (one of our sites lost 20db of effective receiver sensitivity when the antenna is connected) and in the vehicles. And oh my god on portables near electronics indoors. Looking at a spectrum analyzer in my house on low band just shows an insane amount of noise. I gave up on searching low band on my scanner too...it would hang up on noise every few channels. It degrades the use of tone&voice paging too.
Remember, PL only hides the noise. It does nothing to improve the S/N.
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Old 06-30-2017, 10:14 AM
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Originally Posted by R8000 View Post
Can you give us data on these "bribes" you speak of ? Any links to a newspaper article that validates these bribe claims you keep making on RR ?
Engineered coverage (mitigate interference from co-channel users in...other states), frequency reuse, system capacity, housing requirements, equipment availability...all terms benefits concerning higher frequency migration.
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  #35 (permalink)  
Old 06-30-2017, 10:34 AM
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Painting a tower is not going to resolve noise issues. If it is from the tower itself, you will normally will find that there are loose and rusty brackets that are moving with the wind. Add a little moisture and you now have a diode junction that will drive a receiver crazy.

I think that if you look around the site, you will find that a good portion of you noise floor is from IP devices and non shielded interface IP cables between the boxes. If there is a cable TV feed to the site, they are very prone to leakage and cause a real problem.

last place that can cause a bunch of noise is any computer and display that may be left on at the site will drive you crazy trying to locate where the noise is coming from. Between poorly designed IP network devices and everything that goes with it, low band systems are doomed.

I know of a number of 6 meter ham repeaters that had to be shut down due to the high noise floor killing receiver reception. High noise floor problems is a dreaded fear of any low band user today. To add to the problem, most radio shops don't have a clue how to track it down. Many of them don't even own a spectrum analyzer that can help locate the noise source.
When I say the tower needs to be painted, I mean that it is has rust exactly as you describe. I've spent plenty of time poking around sites with a spectrum analyzer. I've unplugged everything including the main breaker powering one entire site and the noise doesn't really stop. I am left to assume that it is due to rusty towers, which are often beyond my control.

Quote:
Originally Posted by Thunderknight View Post
Noise floor is getting atrocious on low band. Both at the sites (one of our sites lost 20db of effective receiver sensitivity when the antenna is connected) and in the vehicles. And oh my god on portables near electronics indoors. Looking at a spectrum analyzer in my house on low band just shows an insane amount of noise. I gave up on searching low band on my scanner too...it would hang up on noise every few channels. It degrades the use of tone&voice paging too.
Remember, PL only hides the noise. It does nothing to improve the S/N.
my good sites have less than a 10dB effective sensitivity loss, bad sites are up to 40dB (which makes them completely useless). In some cases I have one good tower and one bad tower on the same hilltop just a couple hundred feet apart. In at least one other case, a 42MHz receiver is fine while a 33MHz receiver on the same tower is deaf. I'm kind of at a loss and luckily low band isn't my primary band. As I mentioned I installed a voting system for better low band Rx.

I hear some agencies have hired a tower company to do PIM testing (I guess it's more common in the cell world?), but finding a radio shop with knowledge of the situation isn't easy.

Last edited by mrsvensven; 06-30-2017 at 10:43 AM..
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Old 06-30-2017, 12:26 PM
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Originally Posted by mrsvensven View Post
Even if you find a radio that covers that whole split, what are you going to use for an antenna? I have not found any low band antenna with more than 6 or so MHz of bandwidth, and most antennas are much less than that.

Another reason that I'm in the process of abandoning low band is the high noise floor. Many of our sites still work fine, but many are quite deaf. There isn't much rhyme or reason to which sites are fine and which aren't. My current theory is that other transmitters with a high duty cycle (trunked systems and paging) are creating PIM on older towers that may need a paint job.

We used low band for decades, but have recently had to install a voted system to get the same coverage we had in decades past.
1) Motorola had a service bulletin for their wideband Syntor describing a duplexing harness so that two low band antennas, at different frequencies could be connected to one radio. It was basically a cookbook to calculate cable lengths between antennas and a "T" connector.

2) Do you find with your voting system that the low band receivers fluctuate in noise floor? In other words, sites have good and bad days? Is the voting effective?
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Old 06-30-2017, 1:37 PM
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1) Motorola had a service bulletin for their wideband Syntor describing a duplexing harness so that two low band antennas, at different frequencies could be connected to one radio. It was basically a cookbook to calculate cable lengths between antennas and a "T" connector.

2) Do you find with your voting system that the low band receivers fluctuate in noise floor? In other words, sites have good and bad days? Is the voting effective?
I have seen the bulletin, but have not tried it. I imagine that you get a relatively narrow bandwidth on the two frequencies selected.

I don't test my receivers on a daily basis nor do I watch the voter to see what sites are voting. It's simplex so only dispatch listens, so I don't actually listen to it either. When I do PM the sites I generally find that a good site doesn't fluctuate that much, but there is some fluctuation in how bad a bad site is (it's always bad, just to varying degrees).

Prior to the voting system, we would receive complaints on certain days and not others, so some days must have been worse than others. As far as how effective it is, I guess it's as good as any voting system. I'm using all motorola desktrac/maxtrac receivers and the same backhaul so that they have the same audio characteristics. The sites are mostly pretty far apart, I'm covering multiple counties.

Last edited by mrsvensven; 06-30-2017 at 1:44 PM..
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Old 06-30-2017, 1:54 PM
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I have seen the bulletin, but have not tried it. I imagine that you get a relatively narrow bandwidth on the two frequencies selected.

I don't test my receivers on a daily basis nor do I watch the voter to see what sites are voting. It's simplex so only dispatch listens, so I don't actually listen to it either. When I do PM the sites I generally find that a good site doesn't fluctuate that much, but there is some fluctuation in how bad a bad site is (it's always bad, just to varying degrees).

Prior to the voting system, we would receive complaints on certain days and not others, so some days must have been worse than others. As far as how effective it is, I guess it's as good as any voting system. I'm using all motorola desktrac/maxtrac receivers and the same backhaul so that they have the same audio characteristics. The sites are mostly pretty far apart, I'm covering multiple counties.
I was curious because I did the design for the FDOT 47 MHz system here in Florida and selected a voted multicast repeater configuration, A common input frequency for all sites within a zone and voted with JPS SNV-12. We performed a lot of site noise floor evaluations and they varied from day to day. Power line noise seemed to dominate followed by ignition noise.
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Old 06-30-2017, 2:10 PM
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1) Motorola had a service bulletin for their wideband Syntor describing a duplexing harness so that two low band antennas, at different frequencies could be connected to one radio. It was basically a cookbook to calculate cable lengths between antennas and a "T" connector.
This was common with amateur operators using low band Syntors. Had a local guy running a 6 meter whip and a 10 meter whip with this harness to one radio.
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Old 06-30-2017, 2:28 PM
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There were 2 items which Motorola used to extend the bandwidth on VHF low band so that users could get away with 2 antennas.


The Diplex antenna manual and the wideband antenna match.

The diplex manual had the coax dimensions to diplex a radio such as the syntor/x 9000 to 2 low band antennas such as RFI-EMI-GUY mentions.

Additionally there was also a wideband antenna match manual that used to be bundled at one online site along with the diplex antenna manual.


A user could order 2 of the wideband antenna match circuits which consisted of an L/C circuit that was supposed to be attached at the feedpoint of each low band antenna, this effectively extended the VSWR bandwidth of each low band antenna connected to the coaxial diplexer.

I never used the wideband antenna match so I can't say how efficient it was as my antennas were fairly narrowband and centered at 29.4 MHz +- 200Khz and 52 MHz +- 500 KHz which were easily covered with off the shelf quarter wave whips.
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