Motorola R-2550 - how to set the high and low pass filters?

This forum exists for the purposes for discussing service monitors (This includes but is not limited to Motorola, HP, Aeroflex, GD, etc). Additional topics allowed include test procedures, interpretation of test results, where to find information about specific tests, antenna VSWR, return loss testing, duplexer and filter alignment, etc.

Moderator: Queue Moderator

Post Reply
Hightower
Posts: 976
Joined: Mon Sep 24, 2001 4:00 pm

Motorola R-2550 - how to set the high and low pass filters?

Post by Hightower »

For FM deviation measurment, the service manual states in the R-2550/R-2600 specification section:

"Selectable per the following: low pass filters 20Khz, 3Khz, 300Hz & high pass filters 5Hz, 300Hz, 3Khz"

How is these high and low pass filters selected? Nothing in the R2550 owners manual reveals this, so I'm starting to think the R-2550 doesn't have the ability to change these settings, while the R-2600 has this feature.

So lets say there is no way to select the filters on the R2550, what are the default filters set at then?
User avatar
xmo
Moderator
Posts: 2549
Joined: Fri Oct 12, 2001 4:00 pm

Re: Motorola R-2550 - how to set the high and low pass filters?

Post by xmo »

What are your menu choices when you push the "SPF" key?
Hightower
Posts: 976
Joined: Mon Sep 24, 2001 4:00 pm

Re: Motorola R-2550 - how to set the high and low pass filters?

Post by Hightower »

Special Functions Menu:

Version
Remote setup

System Functions
Enable: Generate Mode Speaker
EnableL Auto Switch to Mon if >0.1W
Internal Input: Decoding

Nowhere in these menu items is anything related to audio bandwidth (unless I'm missing something..)
User avatar
xmo
Moderator
Posts: 2549
Joined: Fri Oct 12, 2001 4:00 pm

Re: Motorola R-2550 - how to set the high and low pass filters?

Post by xmo »

On a 2600 there would be more menu choices after: Internal Input Decoding

Display Timeout Interval: 030 min [newer firmware only]
Deviation Level Alarm: 00.0 kHz
High Pass: 5 kHz
Low Pass: 20 kHz [newer firmware defaults to 20, earlier to 3]

-----------------------

The R2550 was a marketing model sold concurrently at the time of the R2600B.

As with several other Motorola products is was created by removing a few features from an otherwise identical product in order to create a less expensive offering. Think Maxar -> Moxy, Mostar -> Traxar, Mitrek - > Motrek.

Up until now, I thought that the only things they had left out of the 2600 feature set were the ability to expand the scope & spectrum analyzer to full screen and the ability to add options [although T.G. was available]

Apparently selectable filters were also deleted. I dug out a 1994 catalog page and there is no mention of filters whereas the corresponding 2600 catalog sheet does mention them.

It is probable that the 2550 comes with 5 Hz and 3 kHz active in narrow band and switches to 20 kHz in wide band.

You could verify that by setting the machine to duplex with zero offset, then while monitoring the unit's own generator use the rotary knob to sweep the audio synthesizer frequency and observe the corresponding receive deviation.
DJP126
Posts: 873
Joined: Wed Jun 18, 2003 6:41 am
What radios do you own?: What's a radio?

Re: Motorola R-2550 - how to set the high and low pass filters?

Post by DJP126 »

Try looking under system functions. They have to be in there someplace so you could properly decode PL or Paging Tones. Another thing you could try is go into monitor mode with the RF display, it might be on the main screen. I guess it's been to long since I've seen one to remember.
Dave
Hightower
Posts: 976
Joined: Mon Sep 24, 2001 4:00 pm

Re: Motorola R-2550 - how to set the high and low pass filters?

Post by Hightower »

DJP126 wrote:Try looking under system functions. They have to be in there someplace so you could properly decode PL or Paging Tones. Another thing you could try is go into monitor mode with the RF display, it might be on the main screen. I guess it's been to long since I've seen one to remember.
Yeah, this is a setting that doesn't get changed too often, so it may be "hidden".

I agree that it should be there to properly decode PL, etc.

Starting to think it maybe some internal physical switches in the service monitor. Will take XMO's advice and try duplex with zero offset.

Will report back with my findings.

Update:

in duplex with 4Khz synth in narrow band:
40Hz = 4.00Khz deviation
500Hz = 4.01Khz deviation
1000Hz = 4.01Khz deviation
1500Hz = 3.90Khz deviation
2000Hz = 3.80Khz deviation
2500Hz = 3.66Khz deviation
3000Hz = 3.22Khz deviation
3500Hz = 2.17Khz deviation


in duplex with 25Khz synth in wide band:
40Hz = 24.5Khz deviation*
1000Hz = 24.5Khz deviation*
4000Hz = 24.5Khz deviation*
10000Hz = 24.5Khz deviation*
19999Hz = 24.5Khz deviation*

* this 24.5Khz is an avarage because the deviation reading is not rock solid per say. It's random between 24.3 - 24.7Khz.

So aligning astro radio TX deviation in wideband mode is not possable due to the fluxiation of the wideband deviation settings. Nor is it possable in narrowband.
Last edited by Hightower on Sun Feb 15, 2009 8:30 pm, edited 1 time in total.
User avatar
xmo
Moderator
Posts: 2549
Joined: Fri Oct 12, 2001 4:00 pm

Re: Motorola R-2550 - how to set the high and low pass filters?

Post by xmo »

I wouldn't hold out any hope of finding any "Filter" choices on any other menus, all of the 2550 screens are really the same as 2600 screens except that omitted features just don't show up.

With regard to decoding - apparently that is another area where features were left out.

The 2600 catalog sheet says it decodes PL, DPL, DTMF, Single tone, 2 tone paging, 5/6 tone paging, Select five, and 20 tone general sequence.

The 2550 catalog sheet says it decodes PL, DPL, and DTMF.

The tone encoding capability of the 2550 is similarly restricted - apparently omitting 2 tone paging, 5/6 tone, select five, and tone remote.

It helps to remember that it was sold at a bargain price:

R2600 - $11,850.00
R2550 - $8,695.00

[1994]
Post Reply

Return to “Test Equipment & RF Equipment Alignment”