BlueClone - The Blue Room's Own Comms System

[pmiller056]

@J Pearce Yes, you can do this. In practice you need really good external filtering on both the transmitter and the receiver to prevent the continuously running transmitter from significantly interfering with the receivers. As an example, 430-440MHz full duplex amateur radio repeaters use a 1.6MHz or 7.6MHz split. They nearly always need to use bulky tuned cavity filters or large antenna separation distances to provide acceptable performance. For temporary/emergency use amateur radio does use wider, non-harmonically related splits such as 145/435MHz or 435/1300MHz which usually requires minimal external filtering. The frequencies I've quoted are used in the UK. Use in other countries will be different.

[themadhippy]

Quote

Yes, you can do this. I

was how the old police radios worked,control in our area was at the top of the fm broadcast range,and the coppers in the field was on,from memory around 140Mhz

[Paul TC]

3 hours ago, themadhippy said:

was how the old police radios worked,control in our area was at the top of the fm broadcast range,and the coppers in the field was on,from memory around 140Mhz

146-148MHz could be a return link from a Hilltop site to a repeater station, not a mobile radio. - See

Ringbell web page on HO Wireless Schemes

[sunray]

1 hour ago, Paul TC said:

146-148MHz could be a return link from a Hilltop site to a repeater station, not a mobile radio. - See

Ringbell web page on HO Wireless Schemes

I think maybe you don't understand how many different systems were in service by the police apart from the 'classic' system you linked to, and more recent systems too.

There was a system where the beat bobby had a receiver, quite often body worn with earpiece and running on UHF plus a separate transmitter on 147-148MHz.

In our area some car systems were transmitting on 152-153MHz and receiving 5.5MHz higher, others on 147-148 and receiving 5.5MHz higher. Many of their car radios also acted as a repeater to UHF for the portable radio when away from their car.

At some stage I have owned a selection of ex-police radios; Pye Ranger, R18 RX, R401RX, T401TX, T4000TX etc base units - Westminster & Reporter mobiles, PF1 pocketphone, Burndept H/H to name but a few with a view to converting them to amateur radio frequencies or music links etc. I currently have several receive filter/distribution amplifier units in service -  designed for 'hill top' receivers on 146-148MHz such as this one which I've retuned to 145MHz for amateur repeater receiver and modified to include the repeater controller:

Sadly zooming in to this from a larger pic the legend on the front isn't legible but I believe this one states 146-148Mhz

[samchurchill]

Hi all, I was pointed in this direction a couple of years ago via 

and, although the requirement at the time was resolved through the purchase of a Tecpro AD903, I’ve now got a new requirement for a twin 4-wire adapter to use with a BMD Constellation HD (which presents its 2 intercom circuits on a single RJ45 socket).  I’d love to be able to follow the previous advice to look at using Bluecom for this, but have a couple of questions…

1) I’ve tried to read through quite a bit of this thread (and the pinned one in this forum) but can’t find any working links to the latest resources including the schematic and parts list.

2) given the schematic, would someone be kind enough to point me in the right direction with which bits wouldn’t be needed for my application, and where I would need to connect my 4-wire cables?

3) if my cut down version is still very similar to the full version, I’ll need a couple of PCBs - does anyone have any spares for sale from a bigger batch?

Thanks!

Edited June 8, 2022 by samchurchill

[Brian]

Is the BMD system compatible with Tecpro? There are a couple of incompatible systems out there. 

[J Pearce]

I made something similar (in a bit of a hurry) using a project box, an XLR4 tail, two 1:1 isolation transformers, and 2 XLR tails. I plugged the XLR4 into a comms pack on the system and used that to do all the complicated electronics. 

A better solution would use an attenuating transformer to better match the line level input to the mic level the comms pack expects. As I was in a rush I just turned down the output that was feeding the box...

[samchurchill]

2 hours ago, Brian said:

Is the BMD system compatible with Tecpro? There are a couple of incompatible systems out there. 

I believe, from reading the BMD manual and a bit of Googling, that it's just two standard 4-wire interfaces, each with a line level input and line level output - is there any reason this wouldn't be compatible with the Tecpro?  (Further details at https://forum.blackmagicdesign.com/viewtopic.php?f=4&t=91276 if anyone is interested.)  In any case, the Tecpro is still in used for the task I posted about a couple of years ago, so I can't free it up and definitely need an additional unit. 

2 hours ago, J Pearce said:

I made something similar (in a bit of a hurry) using a project box, an XLR4 tail, two 1:1 isolation transformers, and 2 XLR tails. I plugged the XLR4 into a comms pack on the system and used that to do all the complicated electronics. 

A better solution would use an attenuating transformer to better match the line level input to the mic level the comms pack expects. As I was in a rush I just turned down the output that was feeding the box...

Yes, that sounds as if it would work but I'm a bit tight on physical space in the rack for 2 additional comms packs as well as an interface project box.  It would also add further cost, which I'm trying to reduce, as we don't have any spare comms packs.

[sdoconnell92]

Hey all, I just found this thread and would love to build some blue com boxes. I wasn't seeing a link to any files in this thread though. Anyone have the schematics?

[dmxlights]

I have the version 1.4 of the beltpack files here http://mcgcs.net/BluecomBeltpack1_4.zip

Edited October 11, 2023 by dmxlights

[boatman]

On 8/7/2023 at 10:22 PM, sdoconnell92 said:

Hey all, I just found this thread and would love to build some blue com boxes. I wasn't seeing a link to any files in this thread though. Anyone have the schematics?

Sorry I missed this post. here's a link to the zip file for version 1.4.