QUADRANT DVB-T

[Pd0hni]

Hello all,

I have been working with 70cm DATV for a few years now and I really like it.
But now I also want to use the QUADRANT DVB-T on 23cm.
Only the preamp I use is not suitable for that.
Does anyone have a good tip for me as to which preamp I should use?
I am looking for a preamp that is suitable for both 70 and 23cm DATV

Regards Jan / Pd0hni

[g0mjw]

Hi Jan

I thought the Quadrant was a transmitter, but I suppose there is a matching RX and for a receiver the pre-amp for 70cm and 23cm would have to contain two bandpass filters. A wideband one won't work well because of all the mobile signals in between. I would look at Wimo's site https://www.wimo.com/en/accessories/ant ... -amplifier - they do do a broadband pre-amplifier.

Now if you want to amplify a TX that's a different story. It depends how much power you need, there are many available, often based on Mini-Circuits modamps, or the obsolete SPG5189, but all of these will need to be used at least 10dB below their maximum output, which in practice means 0-10dBm from a 100mW to 1W device.

I think we need a specification before providing any useful advice.

Mike

[Pd0hni]

Hi Mike,

Thanks for your comment.
It is intended for TX, now I use the "EME162 v2 from Mini Kits" to transmit on 70cm.
And that goes very well.
But the transmitter can also transmit on 23cm, but then I need a preamplifier that can amplify the 23cm power amplifier.
The transmitter of "Antennair DTX1" gives a maximum of -5dB, but I have to go to 150mW/200mW.
This is due to cable length and losses along the way.
The 23cm power amplifier must have 50mW

Jan / Pd0hni

[g0mjw]

Hi Jan

I see - to avoid confusion, we usually call these amplifiers drivers or pre-drivers. If you have -5dBm and need 200mW (23dBm) you are looking for a gain of 30dB or so with some margin. That's possible with one device but more likely two.

If you want to build your own there are some nice designs out there, especially the mini-kits ones, but if you are after a quick simple solution then some of the modules on AliExpress may be suitable. I think you will need two as anything with 30 dB gain on a single board is likely to oscillate unless carefully constructed, which some of these Chinese modules may not be.

Something like this https://www.aliexpress.com/item/1005001871019610.html - the SBB5089+SHF0289 or SBB5089+SHF0589 should be able to give you 100mW, but may be a bit marginal on power output and gain.

A pre-drver gain block like this https://www.aliexpress.com/item/1005005177057814.htm has about 15 dB of gain on 23cm and should be good for 10mW. You would need to put an attenuator after it, as it would over-drive the next stage, but that's desirable for stability as well, 6-10dB.

An alternative, more expensive, but probably better, would be to use the Minikets modules - see here https://www.minikits.com.au/electronic- ... f-wideband - the one you want is probably the MGA-31189 option. It is intended to be used with the DTX-1 and an RA18H1213G

Mike

[Pd0hni]

Hello Mike,

Thanks for your answer.
I'll take a look at this this weekend.
And I will come back to this.

Mike, I have ordered the Mini Kits MGA31189 Driver +24dBm 0.05-2GHz
Thank you for your help.

have a nice weekend
Jan / Pd0hni