I'm looking to make changes, in my shack and one of them is to go with mono band radios via motorola to get rid of the intermod once and for all, its either this or purchase a dualband bandpass filter which run for a minimum of 350$ -Also I'll make use of the dualband radio for my go kit. My budget is at most 250$ for each UHF / VHF, so I guess the question is which one, if it is at all possible 64 channels or 128 preference.
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Best intermod free mobile
- Thread starter wb2rxf
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902
Member
There's never any guarantee of being free from mixing products. You can take some steps to reduce overload, like use filtering ahead of your radio, or padding down the antenna line (deliberately reducing the sensitivity of your system) but even that is catchy.
Once upon a time, when I worked in radio in the NYC area more than 20 years ago, the Hoboken fire department was replacing a Micor base with a Spectra. The Spectra was a desktop base station. Their headquarters was looking right into the World Trade Center at the time, and one of the transmitters on the WTC, and one of the TV stations (more than likely Channel 7) was blasting signal right at them. The Spectra, which most people would say was a great radio at the time - and still is - didn't cut it. What ended up happening is that we rebuilt their Micor, making it more reliable (those things are tanks, anyway), and it was able to more sharply cut out the out-of-band signal than the Spectra was - even when it was installed at Stevens Tech, with a direct view of the WTC. So, it's not always the radio. That Spectra was a fine radio. But the environment for it was wrong.
Right now, a lot of 800 MHz systems are once again being desensed by the cellular A and B carriers putting massive amounts of signal into the street, while the radio has to listen to a relatively weaker public safety control channel or voice channel much further away. The solution will be to reduce the receiver front-end aperture so that only the public safety band comes through, and then move as much public safety as possible out of the respective guard bands. This kind of thing is going to happen every time there's something new coming out. LTE is the latest and greatest, and the carriers want to put them up all over the place to maximize their profits ("it's what they do...").
If you have a radio that works, I would rather invest in a "shape factored filter" that has a response that would attenuate anything that's not inside T-Band (that's what's primarily used around Brooklyn). I would also look at my antennas and make sure there is no rust or corrosion anywhere near them that could be a place where signals would mix. I would also pick out a block of VHF that you want to listen to and put some cans on that, or identify what's blocking your signals and notching it. That could help some if the mixing is in the front-end of your receiver (it can happen there, too!). The good thing, I suppose, is that paging isn't popular anymore. There should be fewer 350 Watt base stations on every street corner blasting 152, 157, and 158 MHz signals.
Good luck. NYC is a tough environment. Always was.
Once upon a time, when I worked in radio in the NYC area more than 20 years ago, the Hoboken fire department was replacing a Micor base with a Spectra. The Spectra was a desktop base station. Their headquarters was looking right into the World Trade Center at the time, and one of the transmitters on the WTC, and one of the TV stations (more than likely Channel 7) was blasting signal right at them. The Spectra, which most people would say was a great radio at the time - and still is - didn't cut it. What ended up happening is that we rebuilt their Micor, making it more reliable (those things are tanks, anyway), and it was able to more sharply cut out the out-of-band signal than the Spectra was - even when it was installed at Stevens Tech, with a direct view of the WTC. So, it's not always the radio. That Spectra was a fine radio. But the environment for it was wrong.
Right now, a lot of 800 MHz systems are once again being desensed by the cellular A and B carriers putting massive amounts of signal into the street, while the radio has to listen to a relatively weaker public safety control channel or voice channel much further away. The solution will be to reduce the receiver front-end aperture so that only the public safety band comes through, and then move as much public safety as possible out of the respective guard bands. This kind of thing is going to happen every time there's something new coming out. LTE is the latest and greatest, and the carriers want to put them up all over the place to maximize their profits ("it's what they do...").
If you have a radio that works, I would rather invest in a "shape factored filter" that has a response that would attenuate anything that's not inside T-Band (that's what's primarily used around Brooklyn). I would also look at my antennas and make sure there is no rust or corrosion anywhere near them that could be a place where signals would mix. I would also pick out a block of VHF that you want to listen to and put some cans on that, or identify what's blocking your signals and notching it. That could help some if the mixing is in the front-end of your receiver (it can happen there, too!). The good thing, I suppose, is that paging isn't popular anymore. There should be fewer 350 Watt base stations on every street corner blasting 152, 157, and 158 MHz signals.
Good luck. NYC is a tough environment. Always was.
K5MPH
Member
Where you live has a lot do do with your signal mixing,one thing i have found out over the years is that the older radios are better when it comes to front end level of filtering,but like 902 said a good filter might do you good,good luck......
Hmm, I understand 902, I'm not technically skilled at building those filters, I'm 1 mile across from the wtc in williamsburg brooklyn, not far from the first stop of the bridge, the intermod was much worse when the old wtc was up, thats when I purchased a bandpass filter for 2 meters / ssb, and it worked so well, If I'd been in the country setting I'd be hearing only the crickets so to speak. I know someone who lives in lower manhattn that uses a kenwood TS 2000 That gets no intermod on 2 meters or 70cm and uses the cx333 as I do, its apples and oranges I understand. I'm also on GMRS & Murs which makes it a bit more complicated, I was under the impression that the motorolas are the king of kings radios. I'll let more folks weigh in and continue to see which is the best fit If my budget went up to get a Motorola MotoTRBO XPR 4550 UHF 403-470 MHz would that solve my issue, or paying more at this point doesn't matter. Just a thought. Thank you to all for your input its greatly appreciated.
N4KVE
Member
Can't beat a MCS2000. Mine never ever made an intermod chirp.
902
Member
Motorola's a very good product, but these days, there are quite a few other very good products from other manufacturers, too (yes, I know it's the Motorola forum).
What might be working to your advantage is all that 900 MHz stuff will no longer be there. 20 years ago, I was looking for a mixing product on top of 1 WTC with a spectrum analyzer and a little yagi antenna. There was so much RF up there that I blew the fuse on the input to the S/A. My solution at the time was to put a smaller antenna (a quarter wave UHF DB-201) on 2 WTC, in the middle of the roof that was surrounded by the observation deck and put a voting receiver inside, then run "house wire" from 2 WTC to 1 WTC just to get a little more isolation. It worked okay, but the old timers would tell me that before the clutter up there, they were able to key up a repeater on top of the WTC with a service monitor from LaGuardia Airport. But over the years, the noise went up and up.
It's probably relatively quiet now. But that could change at some point.
But you could have other sites as potential interferors besides the new WTC, too.
BTW, just got off a social media messenger with a friend who's in Queens and doing GMRS, too. I used to do that when I lived in NJ. Actually had a repeater up on 462.725 years ago.
902
Member
Oh, I'm sorry - I just re-read your reply saying it's worse than the old one!
Well, you don't really build the filters, more than tune them. If you want to stay in the ham bands, the DCI filters have been very good. I would look for used "bandpass" cavities for your GMRS use. The bug is going to be if you are using a repeater. That filter would be tuned to your receive frequency and if you transmit into it at that point, all of your power would be absorbed inside the cavity. You'd need to make up a switching system to switch the filter in and out as needed.
Well, you don't really build the filters, more than tune them. If you want to stay in the ham bands, the DCI filters have been very good. I would look for used "bandpass" cavities for your GMRS use. The bug is going to be if you are using a repeater. That filter would be tuned to your receive frequency and if you transmit into it at that point, all of your power would be absorbed inside the cavity. You'd need to make up a switching system to switch the filter in and out as needed.
Ah yes I had the DCI
For 2 meters for my kenwood TR751a it was a blast not to hear the junk, for weak signal work and the satellites. I had 2 home brew 16 ele beams made with pine wood I bought at home depot, I enjoyed having them vertically polarized & freaking out some people in the Philadelphia area and delaware repeaters when they heard of my antennas and approximately 28 watts. Sorry if I went off the script. I sold my dci a year ago after having it for 15 years to pay off bills. I'm going to pick up a of all modes for 2 meters and 70cm. hence wanting mono banders for vhf uhf fm. Think I lost track here.
For 2 meters for my kenwood TR751a it was a blast not to hear the junk, for weak signal work and the satellites. I had 2 home brew 16 ele beams made with pine wood I bought at home depot, I enjoyed having them vertically polarized & freaking out some people in the Philadelphia area and delaware repeaters when they heard of my antennas and approximately 28 watts. Sorry if I went off the script. I sold my dci a year ago after having it for 15 years to pay off bills. I'm going to pick up a of all modes for 2 meters and 70cm. hence wanting mono banders for vhf uhf fm. Think I lost track here.
Radios with limited band coverage often do better than those that cover a wide frequency range. The Radio Shack HTX 202 was known as one of the best because it only covered the 2 meter band and could not be modified for out of band reception or transmit.
902
Member
Here's the history of that radio. It was actually OEM'd for Radio Shack by Maxon!
http://www.qsl.net/n3sme/htx202.txt
HTX 202
Radio Shack depended on many vendors, and other articles I have read contribute the radio to Icom as the original developer of the design. The battery from the 2 meter Icom of that era fits it and is still available. I have 2 of these radios and also had a commercial Maxon VHF that was a very solid performer on the 2 meter band.
Radio Shack depended on many vendors, and other articles I have read contribute the radio to Icom as the original developer of the design. The battery from the 2 meter Icom of that era fits it and is still available. I have 2 of these radios and also had a commercial Maxon VHF that was a very solid performer on the 2 meter band.
WB2RXF it all depends on the bands you are trying to listen to. You can pick up a CDM1250 on ebay for $150.00 or less with some looking. If you are looking for VHF or UHF single band this is a good unit as it can be programmed under most windows platforms. The radio is limited to 64 channels. The Astro Spectra is probably the next best bet which will be capable of more channels but good ones are hard to find. They had issues with caps in the radios and will eventually fail.
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