Hi All
What is the correct way to increase the RF output power from my Lime Mini?
I wish to use it for DATV on QO-100 I have the Portsdown side all sorted and I have a Spectrian PA to start with ready to go.
The Lime Mini according to the spec sheet gives 0DBM at 2.4Ghz what is the correct way to increase the power output to something usable 1 watt or thereabouts, I have seen articles on people using various Ebay PCB’s using many different type of devices and in some cases cascading them to further increase the output power is there a recommended way to go about this?
73 Keith GU6EFB
Lime Mini increasing output power
Re: Lime Mini increasing output power
Hi Keith
In practice for DVB-S you should expect -4 dBm at 2405 MHz from a Lime Mini at Lime Gain 88.
I use a BGA6489 (about £1 each from RS-online) to take the power up to around +10 dBm. That is all I need for my PA, but under-driven eBay amplifiers are popular for further amplification by other users.
Dave, G8GKQ
In practice for DVB-S you should expect -4 dBm at 2405 MHz from a Lime Mini at Lime Gain 88.
I use a BGA6489 (about £1 each from RS-online) to take the power up to around +10 dBm. That is all I need for my PA, but under-driven eBay amplifiers are popular for further amplification by other users.
Dave, G8GKQ
Re: Lime Mini increasing output power
I am not sure if it is the best way or not, but a couple of stages after the SDR transmitter can mean you are not pushing the Lime or any single stage into compression and keeping amps in linear areas.
For example I am trying a Hackrf and it probably gets to somewhere between -5 dBm and 0dBm at near full output, so I have a low noise amp that has a P1 point at a supposed +19dBm the amp has a gain of circa 14 dBm, So I should be keeping it in the linear region. So I guess it should operate around +14dBm.
Then I have a MHL21336 amp which can give approx 25dB gain with a typical P1 point at +34 dBm so in theory I should be able to get from these two + 34dBm or 2.5 Watts. For a simple carrier it achieved +37dBm, although I have not kept it at that level for long for fear of damage.
For DATV you want the average power to be approx 6dB down from the P1 points on both devices, I believe that 7dB is a typical broadcast standard used on linear amps ( from a co-worker ex BBC ) So for me the average will be at +27/28dBm with the PEP being close to +34dBm. In theory you could continue to work like this up in stages until you get the power level you need to get the signal into the satellite depending on dish size.
Tests into a dummy load on the bench gives me a peak of 60+ watts and things being clean up to 40 Watts without overdoing the side bands by hitting the compression point.
There is one thing I have been paranoid about and it is the spurious signals that can be generated out of the wanted band by an SDR transmitter so I have built a few ID filters to try and limit the signals going into the amps to be at 2.4Ghz. I tend to think the cleaner the signals going in, the cleaner it will be at the output.
For example I am trying a Hackrf and it probably gets to somewhere between -5 dBm and 0dBm at near full output, so I have a low noise amp that has a P1 point at a supposed +19dBm the amp has a gain of circa 14 dBm, So I should be keeping it in the linear region. So I guess it should operate around +14dBm.
Then I have a MHL21336 amp which can give approx 25dB gain with a typical P1 point at +34 dBm so in theory I should be able to get from these two + 34dBm or 2.5 Watts. For a simple carrier it achieved +37dBm, although I have not kept it at that level for long for fear of damage.
For DATV you want the average power to be approx 6dB down from the P1 points on both devices, I believe that 7dB is a typical broadcast standard used on linear amps ( from a co-worker ex BBC ) So for me the average will be at +27/28dBm with the PEP being close to +34dBm. In theory you could continue to work like this up in stages until you get the power level you need to get the signal into the satellite depending on dish size.
Tests into a dummy load on the bench gives me a peak of 60+ watts and things being clean up to 40 Watts without overdoing the side bands by hitting the compression point.
There is one thing I have been paranoid about and it is the spurious signals that can be generated out of the wanted band by an SDR transmitter so I have built a few ID filters to try and limit the signals going into the amps to be at 2.4Ghz. I tend to think the cleaner the signals going in, the cleaner it will be at the output.
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