ARD25 Apco25 decoder & scanning problem...

[Mike_Alpha]

I have an AR8600MKII and I'm thinking of getting the ARD25 Apco decoder.

I understand that the 8600 has to be set to WFM mode to enable the 10.7MHz IF output. As an experiment, I output the 8600's 10.7Mhz IF and put it into my AR8000 set to 10.7Mhz NFM.

All worked well. But I realised that if all frequencies are set to WFM on the 8600, how will it scan, considering the WFM bandwidth is about 75KHz wide?.

This means that unless the frequencies being scanned are 75Khz apart, the scanner will stop on any active frequency within the WFM bandwidth. With 12.5Khz spacing now common, it is going to pose a problem.

Seems like we'll only be able to use the ARD25 in manual VFO mode.

Mike

 

[BANDIT]

I am not sure about your AOR receiver but my Icom R8500 outputs the If in any of the fm modes. FM, FMN, WFM.

 

[mancow]

I'm kind of confused. Why would the mode matter? Isn't the box doing the demodulating prior to it even getting to the radio's detector?


I'm sure there's something I'm missing here.


mancow

 

[Mike_Alpha]

The AR8600's 10.7MHz IF output contains the WFM tuned bandwidth of the receiver before detection. The AR8600 specs say that the WFM filter is 150Khz wide. The tuning is done before the detector, so if the center frequency displayed is 450.000Mhz, then you have 75Khz of open filter either side of that.

The ARD25 obviously has a narrow filter built in, but the problem is with the AR8600 and scanning in WFM mode. If the AR8600 is scanning a bunch of frequencies in WFM mode, it will stop on any signal received within that 150Khz bandwidth, no matter what the programmed frequency is.

So if our programmed frequency is 450.000Mhz and a transmission starts on 450.025, the AR8600 will stop and display 450.000, but the ARD25 will have its narrow filter centered on 450.000, with no signal to decode.

I'm afraid no scanning will be possible when using the ARD25 and the AR8600.

Mike

 

[KC1UA]

Unfortunately there is so little known about this device. I inquired of AOR as to how it worked and they replied to me that the AR8600 was placed in WFM mode because the IF output is WFM only.

However, there is a mod for the 8600 that opens up all mode IF output. I had this mod done for use with a recently acquired SDU5600 spectrum display unit (I'm working on a review for that). I wonder if performing this mod will make the ARD25 and the 8600 "work normally".

AOR is good about quickly responding to inquiries, but I've found that their replies can be somewhat "heiroglyphic" in nature as well. I guess until someone actually gets their hands on one and reports here we'll never know.

I can tell you that the all mode IF modification makes ALL the difference in the world when using the 8600 with the SDU5600. Info for this mod can be found at:

http://www.mods.dk/view.php?ArticleId=2876

It's a matter of moving a zero ohm jumper from one point to another...tiny stuff that requires a steady hand and a lot of patience. A friend of mine well schooled in soldering and desoldering did it for me. I don't know if it would make a difference where the ARD25 is concerned, but it might.

 

[Mike_Alpha]

The WFM modification might do the trick Scott. I knew of the mod, but didn't know what it involved.

As long as we can scan in the NFM or SFM modes, the problem I was originally worried about won't happen.

FYI, this mod does not change the 10.7Mhz IF bandwidth, all it does is enable the WFM circuit (and IF output) no matter what mode the 8600 is in.

As long as the ARD25 is receiving the center frequency displayed, its built-in narrow filter will get rid of any other transmisions within the WFM bandwidth.

Things are looking good again

Mike

 

[KC1UA]

Here's an e-mail I just received from AOR in response to my inquiry about this:

Scott,

Thank you for your e-mail.

Yes, you can set your AR8600 to the NFM mode, and you should
decode APCO25 signals.

Thank you,

AOR USA, INC.

----- Original Message -----
From: Scott Halligan
To: info@aorusa.com
Sent: Friday, June 11, 2004 5:22 PM
Subject: Another ARD25 Question


Hi Folks,

I've done the all-mode IF modification to the AR8600 (original model). In an earlier message, you had indicated to me that the AR8600 would have to be placed in WFM mode for functionality with the ARD25 APCO-25 decoder. Now that the all mode IF mod has been achieved is it possible for me to run the 8600 in NFM and have the ARD25 work properly?

Thanks. Have a good weekend.

Scott - Scan Cape Cod/Scan Massachusetts
http://www.scanmassachusetts.net

 

[Mike_Alpha]

Thanks Scott, now that that's cleared up, does anyone have the info on how to do the all-mode modification on the 8600 MK2??

Mike

 

[n9jjb]

HI.TO ALL.THE NAME HERE IS BILL LIVE IN CHICAGO.
JUST RECEIVE MY ARD 25 DATA RECEIVER TODAY.THE REAR OF THE
ARD 25 HAS ONE BNC CONNECTOR FOR THE IF INPUT.
USING THE SUPPLIED COAXIAL CADLE WITH A BNC CONNECTOR ON EACH END.
LIKE TO KNOW WARE DO PLUG IN MY ANTENNA ON THE R-7000.
THANKS. BILL BUSCH
N9JJB@SBCGLOBAL.NET

 

[SCPD]

LIKE TO KNOW WARE DO PLUG IN MY ANTENNA ON THE R-7000.

Hi Bill;

Plug the antenna lead into the same connector on your R-7000 as you would normally. This is the Icom, right? According to this link below, the radio comes with a 10.7 Mhz IF output (see page 13). Read the note on the 9 volts DC also coming out of this port. You'll want to isolate the ARD25's input somehow.

http://www.icom.co.jp/manual/external/transceivers/IC-R7000.pdf

Regards,
Rick

 

[DougSlug]

Be aware that after you do the all-mode IF modification on the Mk2, there will be a lot more birdies (spurii), which may require adding some PASS frequencies depending on the search ranges you use.