• To anyone looking to acquire commercial radio programming software:

    Please do not make requests for copies of radio programming software which is sold (or was sold) by the manufacturer for any monetary value. All requests will be deleted and a forum infraction issued. Making a request such as this is attempting to engage in software piracy and this forum cannot be involved or associated with this activity. The same goes for any private transaction via Private Message. Even if you attempt to engage in this activity in PM's we will still enforce the forum rules. Your PM's are not private and the administration has the right to read them if there's a hint to criminal activity.

    If you are having trouble legally obtaining software please state so. We do not want any hurt feelings when your vague post is mistaken for a free request. It is YOUR responsibility to properly word your request.

    To obtain Motorola software see the Sticky in the Motorola forum.

    The various other vendors often permit their dealers to sell the software online (i.e., Kenwood). Please use Google or some other search engine to find a dealer that sells the software. Typically each series or individual radio requires its own software package. Often the Kenwood software is less than $100 so don't be a cheapskate; just purchase it.

    For M/A Com/Harris/GE, etc: there are two software packages that program all current and past radios. One package is for conventional programming and the other for trunked programming. The trunked package is in upwards of $2,500. The conventional package is more reasonable though is still several hundred dollars. The benefit is you do not need multiple versions for each radio (unlike Motorola).

    This is a large and very visible forum. We cannot jeopardize the ability to provide the RadioReference services by allowing this activity to occur. Please respect this.

Duplexer, Channel Spacing and Repeater Transmit Power Relationship

Status
Not open for further replies.

gdelacruz

Member
Joined
May 11, 2018
Messages
8
Hello,

I'd like to ask the relationship of the mentioned devices with the following VHF scenario:

1. Tx and Rx spacing at 2.5MHz
2. Repeater 35W (max 50W)
3. Duplexer 50W

Questions:
1. The system is running with duplexer, is it safe to set my Tx power to 50W (max)?
2. Will my Tx saturate my Rx due to narrow frequency spacing?
3. Increasing power to 50W, can it kill my repeater?

Thanks and appreaciate any comment.
 

west-pac

Member
Joined
Nov 13, 2004
Messages
1,686
This is the wrong forum to ask those questions. This forum is for scanners/receivers. There are other forums better suited for transmitters and repeaters.
 

Project25_MASTR

Millennial Graying OBT Guy
Joined
Jun 16, 2013
Messages
4,492
Location
Texas
So...this will really depend on the type of duplexer being used.

The flat pack mobile duplexers need roughly 5 MHz of minimum separation. Various other designs require less. One of the things to consider, the actual isolation capabilities of the duplexer. A 50W rating means that the duplexer is designed to handle 50W of input power. It does not mean the duplexer can adequately isolate 50W of power without desensing the receiver.
 

N5XPM

Member
Joined
Jul 29, 2011
Messages
219
Location
Texas
While we need lots more detail, one key concept is that more power is not usually the answer. A higher antenna installation and lower loss coax usually helps improve performance more than increasing repeater transmit power. Project25_MASTR is on the correct path about repeater receiver performance. Reducing the repeater transmit power may actually improve the repeater performance more than increasing power.
 

prcguy

Member
Premium Subscriber
Joined
Jun 30, 2006
Messages
17,188
Location
So Cal - Richardson, TX - Tewksbury, MA
If the duplexer is rated at 50 watts its certainly a mobile flat pack notch only. 5MHz is about the limit on TX/RX spacing and if you go narrower the notches will cut into the passband and insertion loss will go through the roof plus isolation will suffer.

Depending on the radios used 50w or even 35w can be on the hairy edge of working at 5MHz split with some cheap radios not being able to duplex at all. With a marginal duplexer you have to rely some on the band pass filters in the radio receivers and low noise on the transmitters to avoid desense. At 2.5Mhz its not going to happen with a mobile flat pack and you would need something like a large 4 cavity pass/notch duplexer which can go down to a 1MHz split for some models.
 
Status
Not open for further replies.
Top