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General Scanning Discussion For general questions not specific to a model of scanner or general discussion of use of a scanner. Location specific posts should be directed to the regional forums listed below.

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Old 12-23-2013, 2:46 PM
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Default 1.73mhz

By the title, it looks like this belongs in the am/shortwave dx forum, but it's about police monitoring, so I decided to put it here.

I'm simply looking to satisfy my own curiosity. Years ago, the police abandoned the am broadcast band, and were allocated 1.73mhz. Today, we have very advanced trunking systems and encryption methods using mainly uhf radios as well as some in the vhf high band. In some places however, local governments prefer to use vhf low. Part of this is because the region is crowded with users, but low band also comes in handy in a large county. It takes a whole lot less power to move a 30mhz signal across a county, say 20-30 miles or so, than a 450 or 855 MHz signal.

This having been said, do any of you older guys remember any clingers on to the old 1.73 freq. How late was it used. From what I have seen online, and someone confirm or deny this for me if possible, the 160m ham band doesn't start until about 1.75, and that area is classified as "fixed service", meaning that the stations must be fixed in place. What kind of users are on this freq? That might be an old allocation, and it might be ham now, but it's interesting to know.
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Old 12-23-2013, 2:57 PM
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Actually the 160 band is 1800-2000 khz...as I understand it there are still some fishing buoys and other beacons in the 1700 khz area, but they're dying out in favor of more up to date technology.

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Old 12-23-2013, 4:46 PM
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Quote:
Originally Posted by kc9cra View Post
By the title, it looks like this belongs in the am/shortwave dx forum, but it's about police monitoring, so I decided to put it here.

I'm simply looking to satisfy my own curiosity. Years ago, the police abandoned the am broadcast band, and were allocated 1.73mhz. Today, we have very advanced trunking systems and encryption methods using mainly uhf radios as well as some in the vhf high band. In some places however, local governments prefer to use vhf low. Part of this is because the region is crowded with users, but low band also comes in handy in a large county. It takes a whole lot less power to move a 30mhz signal across a county, say 20-30 miles or so, than a 450 or 855 MHz signal.
Not to be pedantic, but it looks like you are using “mhz” for anything below 30 MHz and “MHz” for anything above 30 MHz. “mhz”, with a small m, would be milliHerz, or one thousandth of a Hz, and I am pretty sure you do not mean 1.73 milliHertz. If you are talking about Millions of cycles per second then the normal usage is MHz, capital M (Mega) and capital H (Hertz being a persons name). Also be aware that in the HF spectrum it is pretty common for frequencies to be expressed in kHz, vs MHz, so that your 1.73 MHz becomes 1730 kHz.

The old police MW band was 1600 to just above 2500 kHz (some locations licensed as high as 3200 kHz, but I don’t find records of operation that high). This was initially one way, from station to police car, to respond the mobile unit would have to stop at a call box. Later some systems used MF station-to-car and VHF car-to-station. As late as 1964 LAPD was still dispatching on 1700 kHz (according to Electric Radio #169, June 2003).

It was because of this usage of medium wave frequencies that LA County and LA City had ordinances restricting the use of short wave radios in cars. The LA County Code of Ordinances is 13.10.010 and 13.10.020, and appears to still be active. It clearly defines short wave to include “between 1600 kilocycles and 2500 kilocycles”. This would make most cars on the road today in violation, since the AM broadcast band has been extended up to 1700 kHz, and most cars today with an AM radio can tune at least that high. Yes, if you are in LA County and have an AM radio in your car you could very possibly be in violation

The Los Angeles City Municipal Code is Sec. 52.44 and it has been re-worded to take any reference to frequency out, currently only saying it is illegal to listen to the police or fire while in a vehicle unless you have a permit to do so.

The traffic heard in the 1600 to 2500 kHz range has changed over the years. As Mike said, float buoys are found there, from 1700 to about 1850 kHz and from 1950 to about 2200 kHz. Notice they encroach on the 160 meter ham band, in the 1800 to 2000 kHz range. Also there are several designated maritime HF frequencies in this range, from 2003.5 kHz up. 2182 kHz is a well known maritime distress frequency, although the US Coast Guard no longer maintains a 24 hour a day watch on that freq. And the 120 meter broadcast band, 2300 to 2495 kHz, is fully within the old Police band., and active with singals every day.

T!

Last edited by Token; 12-23-2013 at 4:49 PM..
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Old 12-23-2013, 5:42 PM
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Quote:
Originally Posted by kc9cra View Post
... Years ago, the police abandoned the am broadcast band, and were allocated 1.73mhz.
I think you are a little confused. 1.73MHz IS the AM broadcast band, but just a bit higher. AM used to end at 1.6MHz or 1600KHz.
In the Boston area we had 4 cities and towns on 1714 KHz. I used to re-tune car radios to pick them up. They were Everett, Needham, Newton and Revere. All the city radios were on the same freq., Police, Fire and Public Works.
When Newton had a fire, before it was announced, they would say, "Fire to Police, can we have the air?". That seemed rather silly because he already had the air.
And we called Everett Fire, the Voice of Doom. One dispatcher had a very low, slow voice. He would say, "Attention Everett Fire Department, Alaaaarm of fire - - - -.
At night we could also hear, I think it was Cleveland, OH on an adjacent freq.
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Old 12-23-2013, 5:50 PM
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Newton had radios as far back as about 1934. When I was going to Grammer school, a cop would park his cruiser at an intersection and do traffic. He would leave the window open to hear calls.
Needham used 1714 until the late 1950s.
Oh, we (Needham) used to reply on the Hi band, fire on 153.95 and Police on 155---.
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Old 12-23-2013, 6:14 PM
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The Detroit MI police used 1700 for one way communications back in the late 50s and early 60s. They were the first police department in the country to use two way portable radios which replaced the 1700 KHz frequency. Since the 60's the Detroit Police transitioned from VHF to UHF and then on to the 800 MHz frequency band, next?
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Old 12-23-2013, 8:16 PM
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Quote:
Originally Posted by DickH View Post
I think you are a little confused. 1.73MHz IS the AM broadcast band, but just a bit higher. AM used to end at 1.6MHz or 1600KHz.
In the Boston area we had 4 cities and towns on 1714 KHz. I used to re-tune car radios to pick them up. They were Everett, Needham, Newton and Revere. All the city radios were on the same freq., Police, Fire and Public Works.
1.73 MHz is not the AM broadcast band, the AM BCB ends now at 1700 kHz, and as you said used to end at 1600 kHz. The police medium wave use in question was outside the AM broadcast band. However, going back further in time you find the police and fire transmitting actually in the AM BCB.

In the 1920ís they were actually sending calls on AM radio stations at times, such as WGN in 1929 and WNYC in 1926. WGN actually dispatched between programming, but this only went on for a few months, roughly March to July 1929.

Police broadcasting moved outside the AM broadcast band after that (to the 1700 to 2500 kHz allocation), using dedicated transmitting equipment instead of leveraging existing stations.

T!
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Old 12-23-2013, 8:39 PM
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Quote:
Originally Posted by ks4ui View Post
The Detroit MI police used 1700 for one way communications back in the late 50s and early 60s. They were the first police department in the country to use two way portable radios which replaced the 1700 KHz frequency. Since the 60's the Detroit Police transitioned from VHF to UHF and then on to the 800 MHz frequency band, next?

In early 1933 Bayonne N.J had 2-way in the 31 and 34 MHz range. I thought these were the first 2-way police units in regular service? Earlier there were some trial runs of medium wave 2-way, with huge wire aerials strung like clothes lines on top of the vehicles.

In the late 40ís (49?) the FCC sets up Public Service bands in the VHF-Hi region, opening the 152-174 MHz range.

T!
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Old 12-24-2013, 12:18 AM
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Here is a history of the Missouri Highway Patrol radio system that I found and on the first page it mentions them using 1674 kHz with 2500 watts during the daytime and 1000 watts at night. Very interesting read.

http://www.mshp.dps.mo.gov/MSHPWeb/P...fCommD_004.pdf

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Old 12-25-2013, 1:38 PM
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Default Yes I remember

Quote:
Originally Posted by kc9cra View Post
By the title, it looks like this belongs in the am/shortwave dx forum, but it's about police monitoring, so I decided to put it here.

I'm simply looking to satisfy my own curiosity. Years ago, the police abandoned the am broadcast band, and were allocated 1.73mhz. Today, we have very advanced trunking systems and encryption methods using mainly uhf radios as well as some in the vhf high band. In some places however, local governments prefer to use vhf low. Part of this is because the region is crowded with users, but low band also comes in handy in a large county. It takes a whole lot less power to move a 30mhz signal across a county, say 20-30 miles or so, than a 450 or 855 MHz signal.

This having been said, do any of you older guys remember any clingers on to the old 1.73 freq. How late was it used. From what I have seen online, and someone confirm or deny this for me if possible, the 160m ham band doesn't start until about 1.75, and that area is classified as "fixed service", meaning that the stations must be fixed in place. What kind of users are on this freq? That might be an old allocation, and it might be ham now, but it's interesting to know.
I used to hear police dispatches between 1600 & 1700 Khz as far back as the early sixties on my Hallicrafters SX-99. Don't know where they were located...somewhere up north because of the accent. Brings back old memories of my early ham radio days.

K4PBN
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Old 12-25-2013, 1:46 PM
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The most recent thing I've heard around 1.73MHz is cordless phones where they split between 1.7 something and 49MHz.
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Old 12-25-2013, 2:11 PM
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Riverside County, California, was active on 1.7 MHz until the early to mid 60's. Remains of the old transmitter and antenna were still on one of the sites as late as the early 1980's.
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Old 12-31-2013, 2:38 AM
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I have an old National NC 98 Radio that has the word Police stamped on the face of the radio. Here is a photo of the radio. http://www.universal-radio.com/used/un10disp.jpg
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Old 02-09-2014, 2:10 AM
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Quote:
Originally Posted by prcguy
The most recent thing I've heard around 1.73MHz is cordless phones where they split between 1.7 something and 49MHz.
I would LOVE finding one of these phones!!

THEY WERE THE BEST EVER MADE!!!!!!! -- Had the best range and were quite awesome!!!!!

Only 2 different makes of analog cordless phones were any good.....

1) The 1.7Mhz phones (FM side of the frequency)
2) The 46Mhz phones.....

Everything after #2 was crap and still is!!!!!!!!
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Old 02-09-2014, 4:39 AM
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Wirelessly posted (Opera/9.80 (BREW; Opera Mini/6.0.3/27.2354; U; en) Presto/2.8.119 320X240 LG VN530)

IIRC, the 1.73MHz cordless phones used that band for base-to-handset, and 49MHz for handset-to-base.
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Old 02-09-2014, 10:27 PM
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Did they all do that?? (All of the 1.7Mhz phones used 49 for input? (Same as 46Mhz phones))
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Old 02-11-2014, 12:21 AM
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LOL @ Dude111. You're so concerned about security that you still use Windows 98 thinking the NSA can't tap it or something and you think 45MHz phones are good? Any scanner or some baby monitors can pick up the damn things. Back when I had one of those 45 MHz phones I got nothing but static and fade and when I keyed up on the CB there would be bleed through.

Best phone you can buy now is an EnGenius phone. They use encrypted TDMA and have a very long distance, but are pretty pricy. The next best would either be a DSS or DECT 6.0. If you go DECT 6.0 you need to make sure it's encrypted as you can use Backtrack to decode DECT 6.0. Although the encryption is weak on a DECT 6.0 phone.

Anyway, if you want a phone in the 45 MHZ range try a second hand store and eBay for a battery or eBay for both.
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Old 02-11-2014, 12:53 AM
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Yes I know but the sound quality IS BETTER being analogue! (I dont think I would make any serious calls on it JUST IN CASE)
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