Hi All,
I'm looking for preamplifier to fit my ( Antennair Quadrant DVB ) transmitter on 436Mhz
According to the manual the output is max -5dbm = 0.3mW that is not much.
But I need to feed the end 60W amplifier with at least 100mW ore more.
Who can help me find a preamplifier that will work on 0.3mW and giv me at least 100mW
Any suggestion is welkom.
Pd0hni
Preamplifier
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Re: Preamplifier
Are the power ratings you gave for the amplifier in SSB, FM or DATV use?
A 60W SSB amplifier will not be capable of more than around 12W output using DVB-S; therefore you would need 20mW of DATV drive. A preamp with a gain of around 18dB would get 0.3mW up to 20mW.
I've used these https://amzn.eu/d/il4eQSr with the DTX1 (Antennair) and also a Pluto and a Lime Mini.
Their gain varies depending on the band in use but I get around 15dB at 23cms. If you don't get enough drive with one you can always use a pair in cascade and either fit attenuators between them or reduce the drive from the DTX1 to get the level you want.
DATV output maximum is about 80mW before significant distortion ocurrs.
At around 6 euro you can't go wrong.
Clive G3GJA
A 60W SSB amplifier will not be capable of more than around 12W output using DVB-S; therefore you would need 20mW of DATV drive. A preamp with a gain of around 18dB would get 0.3mW up to 20mW.
I've used these https://amzn.eu/d/il4eQSr with the DTX1 (Antennair) and also a Pluto and a Lime Mini.
Their gain varies depending on the band in use but I get around 15dB at 23cms. If you don't get enough drive with one you can always use a pair in cascade and either fit attenuators between them or reduce the drive from the DTX1 to get the level you want.
DATV output maximum is about 80mW before significant distortion ocurrs.
At around 6 euro you can't go wrong.
Clive G3GJA
Re: Preamplifier
Hi Clive,
Thank you for the replay.
The signal is used to transmit DATV at 436Mhz 70cm band.
At the moment I use a "Minikits" preamp that starts with a input off 0dbm and gives me about 100mW. ( I'm not able to measure )
The 60W amplifier that I use is build with a RA60H4452 from R.Zech from Germany, and will work great between 20 to 30mW (max 50mW )
But I'm planning to put the amplifier further away 15meter because of the noise of the fan 2x. ( signal loss over the cable )
That is way I'm looking for a new TX preamp that is slightly better.
Jan / PD0HNI
Thank you for the replay.
The signal is used to transmit DATV at 436Mhz 70cm band.
At the moment I use a "Minikits" preamp that starts with a input off 0dbm and gives me about 100mW. ( I'm not able to measure )
The 60W amplifier that I use is build with a RA60H4452 from R.Zech from Germany, and will work great between 20 to 30mW (max 50mW )
But I'm planning to put the amplifier further away 15meter because of the noise of the fan 2x. ( signal loss over the cable )
That is way I'm looking for a new TX preamp that is slightly better.
Jan / PD0HNI
Re: Preamplifier
Hi Jan
Put one of the SPF5189z modules at each end of your 15m feeder. That will give you enough gain to counter the loss in the feeder (you could use 5mm dia. coax).
Your RA60H4452 module is unlikely to achieve the 30dB gain claimed in the datasheet as 70cms is outside its intended range. The extra gain of two modules will give you gain to spare.
Clive G3GJA
Put one of the SPF5189z modules at each end of your 15m feeder. That will give you enough gain to counter the loss in the feeder (you could use 5mm dia. coax).
Your RA60H4452 module is unlikely to achieve the 30dB gain claimed in the datasheet as 70cms is outside its intended range. The extra gain of two modules will give you gain to spare.
Clive G3GJA
Re: Preamplifier
Hi Clive,
That is a good idee.
I will keep this in mind, it is a possibility I did not think off.
The cable I use is 10mm H2000 flex
Thanks a lot.
Jan / PD0HNI
That is a good idee.
I will keep this in mind, it is a possibility I did not think off.
The cable I use is 10mm H2000 flex
Thanks a lot.
Jan / PD0HNI