Home Amateur Radio Uniden MR8100 Scanner

Uniden MR8100 Scanner

by MD0MDI
Old Uniden MR8100 Scanner

I was introduced to this scanner some time back by Morgan (MD0DXW) who has had one of these for some time to listen to the aircraft band which he enjoys, and although I don’t do much as far as listening nowadays, I thought that this was quite a nice unit, and it would be well suited to the Land Rover when it is finished.

Only problem, is no instructions (didn’t expect any) and no idea how to use it, thus me putting this page together to help others that may come across this scanner in their travels…

Before I get into all the normal boring stuff that I have located on the internet, here is a link to my web page on diagnosing and repairing the couple of faults that I have with the unit:

Most of the information found here has been found on other websites, especially www.repeater-builder.com which was thankfully very helpful, but besides this and the Yahoo Group, there is really not a lot around for this model of Uniden Scanner…

Technical Specifications

 

  • Band Coverage: 12 bands (see the frequency chart below)
  • Channels & Banks: 10 channels per bank, 10 banks, total 100 channels
  • Scanning Speeds: 2 speeds.
    • [TURBO SCAN] – 93 channels/sec
    • [   SCAN   ] – 32 channels/sec

    Actual speed depends on how channels are programmed.

  • Sensitivity: Typically, less than 1 µV at 12 dB SINAD for all bands
  • Intermediate Frequencies: 10.85 MHz, 450 kHz.
  • Adjacent Channel Rejection: 70 dB at 25 kHz, 40.84 MHz rcve. freq.
  • Intermodulation: 60 dB, 162.4 MHz rcve. freq.
  • Ultimate Signal to Noise: 45 dB, 40.84 MHz rcve. freq.
  • Audio Response: -6 dB per octave, + 1–3 dB, ref. 1 kHz (200 to 3500 Hz)
  • Audio Power: 3.0 W minimum into 4 ohm speaker.
  • Speaker: External 6 W speaker included.
  • Operating Temperature: -20° to 60° C (-4° to 140° F)
  • Storage Temperature: -30° to 70° C (-22° to 158° F)
  • Power Requirements: Nominal 10–14 VDC, 0.8 A
  • Antenna Jack: 1 BNC for all bands, 50 ohm
  • Size: 20.0 × 14.6 × 4.8 cm (7.87”W × 5.75”H × 1.89”D)
  • Weight: 1.0 kg (2.1 lbs)
  • Mounting: Dash top or wall mount. Mounting bracket included. Does not include antenna.

Physical Layout

Uniden MR8100 Scanner Front Panel Information

1. On/Off Switch – Turns the Scanner On and Off!

2. Volume Control Switch – Turns the Scanner On and Off, and Adjusts the desired listening level.

3. Squelch Control – Adjust to quiet the scanner and keep it scanning until a signal is received.

4. Contrast Control – Adjust the viewing angle of the LCD.

5. DIM Control – Adjust the backlight of the display and the keyboard.

6. Channel Number – Displays the current channel number.

7. Display – Displays the Channel Identity and Prompt messages when in Programming mode.

8. P Indicator – Indicates the Priority Channel when lit.

9. Bank Indicators – Displays active bank or banks when lit.

10. Hold Indicators – Hold mode when lit (Not Scanning).

11. Scan Indicators – Scan Mode when lit.

12. Pri Indicator – Indicators Priority Sampling when lit.

13. L/O Indicator – Lit when selected channel is not in the scan sequence.

14. PROG Indicator – Indicates when you are in Programming Mode.

15. Number Keys – Used to program frequencies into memory, also used to select and deselect memory banks.

16. Decimal Key – Used to place a decimal point into the display when in program mode.

17. Enter Key – Used to enter frequencies into scan memory.

18. L/O Key – Used to Add or Delete a channel from the scan sequence.

19. SCN Key – Used to override signals, to scan through selected channels.

20. SPD Key – Used to change between33 channels per second and up to 100 channels per second scanning.

21. PRG Key – Used to enter or leave Program Mode.

22. HLD Key – Used to stop scanning or advance through active banks.

23. MAN Key – Used to stop scanning and enter into direct channel access mode.

24. PRI Key – Used to select or deselect priority sample.

25. Antenna Connection

26. Power Connection

27. Extension Speaker

Band Coverage

Band Coverage (MHz)Channel Spacing (kHz)Sensitivity: 12 dB SINAD (µV)
29 – 29.750.4
29.7 – 5050.4
50 – 5450.4
118 – 13650.7
136 – 14450.5
144 – 14850.5
148 – 17450.5
406 – 42012.50.5
420 – 45012.50.5
450 – 47012.50.5
470 – 51212.50.5
806 – 95612.50.6

Prohibited ranges (inclusive), enabled through password:

RangeDescription
824.0000 – 849.0000TV 72 – 76, Cellular – mobile
869.0000 – 894.0000TV 80 – 83, Cellular – base

Useful Downloads

Here is the User Manual for the Uniden MR8100

Uniden MR8100 - Owners Manual

Uniden MR8100 – Owners Manual

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694.72 KB 11 downloads

I have not been able to locate any other software (that is free) to program the Uniden MR8100 but the one that Uniden provided, it is I am afraid, far from user friendly and requires a MS-DOS environment to work.

Uniden Scan Software for MS-DOS

Uniden Scan Software for MS-DOS

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46.97 KB 15 downloads

Desperately Wanted – Service Manual and Schematics

Some useful notes on the software…

  • Compiler used: Microsoft BASIC, Copyright 1988 Microsoft Corporation
  • Program written by: Copyright 1989 SPAN, Inc. REV 5
  • Acknowledgement: UNIDEN CORP 1989
  • Communication protocol: COM1,1200,N,8,1,CS2000,DS,CD
  • Special character commands:
    • Ctrl Alt C – exit program
    • Ctrl Alt P – enter password “ENTER CODE:”.
  • Program imposed frequency limits prevent tuning within certain ranges. Here are the permitted ranges (inclusive):
CoveredNot Covered 
29.0000 – 54.0000
54 – 118TV channels 3 – 6, FM Broadcast 88 – 108 (see note), Aircraft communications IR 112 – 118 MHZ (see note)
118.0000 – 174.0000
174 – 406TV channels 7 – 13, 222 – 225 Amateur radio, 225 – 406 Military (mostly aircraft, mostly AM)
406.0000 – 512.0000
512 – 806TV 20 – 69
806.0000 – 956.0000

Data Port Parameters

Baud RateParityData BitsStop Bits
1200NONE81

NOTE: Data can not be sent to the radio if it happens to be locked on to the priority channel. Make sure the Priority indicator is off (press ‘PRI’).

Every character sent to the radio is echoed back to the PC. It is therefore important to always flush the input buffer and “confirm” the received characters match those sent.

There are two types of commands that can be sent to the radio:

1Program a Channel / Bank Label / Priority; (send 21 bytes):    
2Request data from the radio; (send 3 bytes):    
– then the radio responds with 18 bytes:

Where the <CC>, <DD>, and <EE> are single byte values 20410, 22110, and 23810 respectively.

In the table above, the <type> (1 byte): is one of 3 choices: Priority or Bank Label or Channel

  • <0x> – Priority; <data>; (4 bytes): <bc>, <?>, <bank 1–8>, <bank 9,10>
    This sets or shows the priority channel assignment and the current active banks. Also sets or shows 16 character “hidden” text for auxilliary usage.
  • <bc> see below
  • <?>: 0 (unknown)
  • <bank 1–8>; (1 byte): bits are as follows:
    • <0> – bank 5
    • <1> – bank 6
    • <2> – bank 7
    • <3> – bank 8
    • <4> – bank 1
    • <5> – bank 2
    • <6> – bank 3
    • <7> – bank 4
  • <bank 9,10>; (1 byte): bits are as follows:
    • <0> – ? (default to 0)
    • <1> – ? (default to 0)
    • <2> – ? (default to 0)
    • <3> – ? (default to 0)
    • <4> – bank 9
    • <5> – bank 10
    • <6> – ? (default to 0)
    • <7> – ? (default to 1)
  • <Bb> – Bank Label; <data>; (4 bytes): 0, 0, 0, 0
    This sets or shows the text associated with the bank. This is displayed briefly when a bank is switched to “active” during scanning by pressing a number key.
  • <bc> – Channel; <data>; (4 bytes): <flags>, <band>, <freq1>, <freq2>
    This sets or shows the channel frequency and additional attributes. Text may be numeric representation of frequency or any arbitrary channel label.
  • <flags>; (1 byte):

Bit(s)Description
<3:0>0 (unknown)
<4>channel is not locked out: 0, channel is locked out: 1
<5>not USED: 0, USED: 1
<6>not SECURE: 0, SECURE: 1
<7>0 (unknown)

  • Not USED means that channel can not be unlocked from the keyboard unless a new frequency is programmed.
  • SECURE means that channel can not be altered from the keyboard.

 

<band>; (1 byte):

Bit(s)Description<0>IF shift: set to 1 for band 0, otherwise 0 for other bands<1>set to 1 for 118–135.995, otherwise 0 (this may be the AM / FM switch)<3:2>0: 29 – 135.995 MHz (5 kHz spacing, 0.4 µV sensitivity)
1: 136 – 174 MHz (5 kHz spacing, 0.5 µV sensitivity)
2: 406 – 512 MHz (12.5 kHz spacing, 0.5 µV sensitivity)
3: 806 – 956 MHz (12.5 kHz spacing, 0.6 µV sensitivity)<4>12.5 kHz decrement (range 806 – 956 MHz, see below)<7:5>0 (unknown)

<freq1>, <freq2>; (total 2 bytes):
This is a 16 bit unsigned integer – most significant byte followed by least significant byte.

This integer is calculated from the frequency. There are three different calculations depending on the band in which the frequency lies.

equencyband byteFormulaResult IntegerTheoreticalChannel Step
in MHz<3:2><0>Frequency Range
29 – 135.99501F × 200 + 21707970 – 29369-10.85 – 316.82505 kHz
136 – 17410F × 200 – 217025030 – 3263010.85 – 338.52505 kHz
406 – 51220F × 80 – 86831612 – 4009210.85 – 830.037512.5 kHz
806 – 956 *3031806 – 3780610.85 – 1649.225012.5 kHz

* For the range 806 – 956 MHz perform the additional calculations with the result integer:

  1. If integer is odd – add 1 to it, set bit <4> of band byte.
  2. Divide the integer by 2 (always)

Note: according to specifications, 10.85 MHz is the receivers intermediate frequency.

Where <0x>, <bc> and <Bb> are bytes containing the following nibbles (4 bits):

  • x – arbitrary value
  • B – actual hex (11 decimal)
  • b – bank number 1 to 10 (1 – A16)
  • c – channel number 1 to 10 (1 – A16)

    1. Characters 0 – 6 shift left by 1
    2. Vacated bit <0> of these characters is transposed character 7: bits <6> to <0> respectively
    3. Characters 8 – 14 shift left by 1
    4. Vacated bit <0> of these characters is transposed character 15: bits <6> to <0> respectively<text>; (14 bytes)…16 ASCII characters are “compressed” to 14 data bytes. This is possible because only 7 out of 8 bits per byte are used (value 0 to 127). Because the high bit <7> is always 0 (unused) the bytes are left-shifted. The vacated least significant bit <0> is then used to squeeze in an extra character longitudinally. In summary:

Allowable characters in text are ASCII in the range 3210 to 12710, with the following exceptions:

CharacterDecimalDisplayed as
\92¥ (yen)
~126(right arrow)
(del)127(left arrow)

  • There are no descenders for the letters: g, j, p, q, y. They do not display well.

After sending data to the radio, unlock it (continue scanning) by sending a 0 byte.

Technical Observations on the Uniden MR8100 Firmware and Programming Software

 

  • Only 16 characters of the 20 character display can be programmed. The first 4 characters are reserved as follows:
    • character 1 – shows ‘P’ for a priority channel indicator, otherwise it is blank
    • character 2 and 3 – shows channel number “ 1” to “10
    • character 4 – is always a blank separator
    • There is no indication of the bank number in the display.
  • The text shown when enabling a bank for scanning such as “     BANK 1     ” is programmable via the computer software. Something more descriptive might be: “2m HAM    BANK 1
  • It is not known at this point whether the text “       SCAN      ” or “   TURBO SCAN   ” can be changed.
  • There is a 16 character text message (not visible) programmed via computer during the assignment of the priority channel. Uniden’s software uses “UNIDEN CORP 1989”. Other text may be substituted by custom software for identification purposes, such as date of last download, etc.
  • Cellular phone frequencies in the range 824 to 849 MHz and 869 to 894 MHz can only be programmed by software (not front panel). There may be a hardware or software solution to enable this range via front panel. Clue: a flyer states “Control of field programming options”… “field accessibility to cellular phone band”. This has not been confirmed. Uniden’s software protects this range via password, requiring the signing of a non-disclosure agreement.
  • The hardware does not restrict frequency range. The scanner can be programmed for TV audio, FM broadcasts, aviation bands, etc. via custom software. Unfortunately the scanner only receives in FM-narrow mode. FM-wide signals such as broadcast, or AM signals such as aviation thus can not be clearly discernable. The only practical benefit of this “unlimited” range may be the reception of the 222 – 225 MHz HAM band adn perhaps military communications is the 225 – 406 MHz range.
  • The manual claims a scanning rate up to 100 channels per second. A flyer claims a top speed of 93 channels per second “depends on how channels are programmed”. There is no clue offered by Uniden as to how to optimize scanning speed. This has to be investigated.
  • The 2 second scan delay (resume scanning) might be programmable to other delay times. This has not been confirmed.
  • Specifications in the manual list 5 kHz and 12.5 kHz channel spacing. This spacing was thought to be irrelevant since the scanner can be programmed for any frequency to a 1 kHz resolution from the front panel. At least the text display shows that. In reality, the frequencies entered are rounded to the nearest channel spacing. The display is misleading.
  • There is no way to determine the frequency of programmed channels unless the 16 character text message shows it. This is not a problem for frequencies entered from the front panel as the text is automatically set to contain “nnn.nnnn MHZ    ”. However, for frequencies programmed via computer where the text message could contain other information such as station call sign or city of origin, the user can not extract the actual frequency using the front panel of the scanner. This is perhaps a security feature which prevents unauthorized identification of pre-programmed frequencies.
  • The manual warns of birdies. No list of known birdies is supplied by the manufacturer. However, through exhaustive testing one was obtained. See Birdie List.
  • Confirmed available and theoretically available frequencies:

Frequency RangeFront PanelUNIDEN softwareCustom SoftwareBand Bits
LowerUpper<3:2><1>
028.995Y
2954YYY00
54.005117.995Y0?
118135.995YYY01
136174YYY10
174.005405.995Y??
406512YYY20
512.005805.995Y??
806823.9875YYY30
824848.9875passwordY30
849868.9875YYY30
869893.9875passwordY30
984956YYY30
956.01251649.225Possibly??
(see note)

The firmware in the receiver microprocessor enforces the front panel limits. The firmware can probably be modified.
The data format can in theory support frequencies up to 1.6 GHz. The RF section in the scanner receiver probably limits this.

  • Uploading the entire file to the scanner should take 39 seconds minimum. In practice, it takes 63 seconds. (UNIDEN software takes 87)
    • (111 × 21 × 2) ÷ 120 = 39 seconds
  • Downloading the entire file from the scanner should take 22 seconds minimum. (UNIDEN software takes 24)
    • (111 × 24) ÷ 120 = 22 seconds

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