4.5v software switched Bias-Tee from HF+?


Ruben Navarro Huedo (EA5BZ)
 

Hello:
Can we have 4.5v software switched Bias-Tee from HF+?
Tnx a lot.


Ruben Navarro Huedo (EA5BZ)
 

Mainly on VHF is needed.


prog
 
Edited

On Sat, Nov 11, 2017 at 08:00 am, Ruben Navarro Huedo (EA5BZ) wrote:
Hello:
Can we have 4.5v software switched Bias-Tee from HF+?
Tnx a lot.
The bias tee was not included in the HF+ and here's the reasoning behind it:
  • You will never need a LNA on HF with the current MDS (-140 dBm @ 50 ohms at max gain)
  • The MDS on VHF is also very low (-141 dBm @ 50 ohms at max gain) and sufficient for most real world use-cases
  • Adding a bias-tee will cost a few dB's of MDS
  • Even if you need lower MDS on VHF, to maintain the linearity of your system you will need a LNA that draw a lot of current, and probably operates at voltages greater than 4.5v
    • It is not recommended to power such LNA from USB
Of course, the situation is different with mid-range SDR's, but we are not in that segment for the HF+.
Don't worry, it will just work :-)


Ruben Navarro Huedo (EA5BZ)
 

TNX for your answer.

I own a LNA + BPF ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 ) for 137.5 mhz.
This is why i was asking for  BIAS-T.

I use around 30 meters of ECOFLEX-10 between my antenna and SDR.

I will try it when received without LNA and BPF.


Simon Brown
 

Ruben,

 

You really, really, really don’t need either a BPF or LNA with the HF+ at 137 MHz.

 

Simon Brown, G4ELI

 

www.dxgalaxy.com
www.sdr-radio.com
www.sdr-satellites.com

 

 

From: main@airspy.groups.io [mailto:main@airspy.groups.io] On Behalf Of Ruben Navarro Huedo (EA5BZ)
Sent: 11 November 2017 16:40
To: main@airspy.groups.io
Subject: Re: [airspy] 4.5v software switched Bias-Tee from HF+?

 

TNX for your answer.

I own a LNA + BPF ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 ) for 137.5 mhz.
This is why i was asking for  BIAS-T.

I use around 30 meters of ECOFLEX-10 between my antenna and SDR.

I will try it when received without LNA and BPF.


jdow
 

Um, 35 to 50 meters of RF cable out to the antenna is a lot of loss that could be made up with a relatively low gain amplifier restoring a low noise figure.

There is always a case for an LNA, although darned few people really need to worry about it. I think back on the breathless prose describing the LNA used on the fancy horn antenna for bouncing telco signals around with the ECHO satellite. That's when the scientists found the left over noise from the big bang. Anybody else remember reading about that sugar scoop antenna? Like I say, really specialized uses might need it. But mere mortals like most of us won't.

{^_-}

On 2017-11-11 13:30, Simon Brown wrote:
Ruben,
You really, really, really don’t need either a BPF or LNA with the HF+ at 137 MHz.
Simon Brown, G4ELI
www.dxgalaxy.com <http://www.dxgalaxy.com/>
www.sdr-radio.com <http://www.sdr-radio.com/>
www.sdr-satellites.com <http://www.sdr-satellites.com>
*From:*main@airspy.groups.io [mailto:main@airspy.groups.io] *On Behalf Of *Ruben Navarro Huedo (EA5BZ)
*Sent:* 11 November 2017 16:40
*To:* main@airspy.groups.io
*Subject:* Re: [airspy] 4.5v software switched Bias-Tee from HF+?
TNX for your answer.
I own a LNA + BPF ( https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94 ) for 137.5 mhz.
This is why i was asking for  BIAS-T.
I use around 30 meters of ECOFLEX-10 between my antenna and SDR.
I will try it when received without LNA and BPF.


prog
 

On Sat, Nov 11, 2017 at 02:15 pm, jdow wrote:
Um, 35 to 50 meters of RF cable out to the antenna is a lot of loss that could be made up with a relatively low gain amplifier restoring a low noise figure.

There is always a case for an LNA, although darned few people really need to worry about it. I think back on the breathless prose describing the LNA used on the fancy horn antenna for bouncing telco signals around with the ECHO satellite. That's when the scientists found the left over noise from the big bang. Anybody else remember reading about that sugar scoop antenna? Like I say, really specialized uses might need it. But mere mortals like most of us won't.

{^_-}
This falls in the 3rd point of my mail. If such LNA is required, you really don't want to power it from USB. We are talking big IP3 here.


Joe M.
 

For the minority who need LNAs, they can also add a DC
insertion device or power them separately from the coax.

I agree "punishing" those who don't need Bias-T with
additional loss is not something that should be done.

Joe M.

On 11/11/2017 5:15 PM, jdow wrote:
Um, 35 to 50 meters of RF cable out to the antenna is a lot of loss that
could be made up with a relatively low gain amplifier restoring a low
noise figure.

There is always a case for an LNA, although darned few people really
need to worry about it. I think back on the breathless prose describing
the LNA used on the fancy horn antenna for bouncing telco signals around
with the ECHO satellite. That's when the scientists found the left over
noise from the big bang. Anybody else remember reading about that sugar
scoop antenna? Like I say, really specialized uses might need it. But
mere mortals like most of us won't.

{^_-}

On 2017-11-11 13:30, Simon Brown wrote:
Ruben,

You really, really, really don’t need either a BPF or LNA with the HF+
at 137 MHz.

Simon Brown, G4ELI

www.dxgalaxy.com <http://www.dxgalaxy.com/>
www.sdr-radio.com <http://www.sdr-radio.com/>
www.sdr-satellites.com <http://www.sdr-satellites.com>

*From:*main@airspy.groups.io [mailto:main@airspy.groups.io] *On Behalf
Of *Ruben Navarro Huedo (EA5BZ)
*Sent:* 11 November 2017 16:40
*To:* main@airspy.groups.io
*Subject:* Re: [airspy] 4.5v software switched Bias-Tee from HF+?

TNX for your answer.

I own a LNA + BPF (
https://store.uputronics.com/index.php?route=product/product&path=59&product_id=94
) for 137.5 mhz.
This is why i was asking for BIAS-T.

I use around 30 meters of ECOFLEX-10 between my antenna and SDR.

I will try it when received without LNA and BPF.



---
This email has been checked for viruses by AVG.
http://www.avg.com


Simon Brown
 

FWIW I have 25m of good coax, using the LNA 5000 from SSB Electronics seriously degraded the received signals, I do mean *seriously*. Coax: https://messi.it/en/catalogue/50-ohm-cables-ham-radio/broad-pro-50-double-jacket.htm If you're going to use a serious LNA then it'll require a separate 12v feed.

As for a BPF with the HF+: "You're having a Turkish".

Simon Brown, G4ELI

www.dxgalaxy.com
www.sdr-radio.com
www.sdr-satellites.com

-----Original Message-----
From: main@airspy.groups.io [mailto:main@airspy.groups.io] On Behalf Of Joe M.
Sent: 11 November 2017 23:54
To: main@airspy.groups.io
Subject: Re: [airspy] 4.5v software switched Bias-Tee from HF+?

For the minority who need LNAs, they can also add a DC insertion device or power them separately from the coax.

I agree "punishing" those who don't need Bias-T with additional loss is not something that should be done.

Joe M.


jdow
 

20 dB is enough to do that.
{^_^}

On 2017-11-12 00:32, Simon Brown wrote:
FWIW I have 25m of good coax, using the LNA 5000 from SSB Electronics seriously degraded the received signals, I do mean *seriously*. Coax: https://messi.it/en/catalogue/50-ohm-cables-ham-radio/broad-pro-50-double-jacket.htm If you're going to use a serious LNA then it'll require a separate 12v feed.
As for a BPF with the HF+: "You're having a Turkish".
Simon Brown, G4ELI
www.dxgalaxy.com
www.sdr-radio.com
www.sdr-satellites.com
-----Original Message-----
From: main@airspy.groups.io [mailto:main@airspy.groups.io] On Behalf Of Joe M.
Sent: 11 November 2017 23:54
To: main@airspy.groups.io
Subject: Re: [airspy] 4.5v software switched Bias-Tee from HF+?
For the minority who need LNAs, they can also add a DC insertion device or power them separately from the coax.
I agree "punishing" those who don't need Bias-T with additional loss is not something that should be done.
Joe M.


Eric Oyen <eric.oyen@...>
 

ok,
there are a number of solutions to getting max signal to the SDR.
1. mount at the antenna feed point. this will require remote power feed, a weather sealed box and a remote machine. Believe me, USB can't transport signals to the machine much past 12 feet (too much delay) so having a weather sealed machine close by won't hurt.

2. long run of very low coax (rg-6 works up to 1200 Mhz with fairly low loss). btw, there is a low cost LNA out there that can be powered on a USB connection. I ordered one earlier this year to use with one of my USB RTL-SDR dongles. it has good overload protection and adds only .5 Db insertion noise for 30 Db signal gain from 100 Khz to 5 Ghz. the thing is about the size of 4 postage stamps. this would be a good solution for long runs of coax.

so, unless you are doing anything above 500 Mhz, coax loss isn't going to be much of a factor. Thus, using the onboard LNA just seems like adding extra complication and noise.

DE n7zzt Eric

On Nov 12, 2017, at 1:32 AM, Simon Brown wrote:

FWIW I have 25m of good coax, using the LNA 5000 from SSB Electronics seriously degraded the received signals, I do mean *seriously*. Coax: https://messi.it/en/catalogue/50-ohm-cables-ham-radio/broad-pro-50-double-jacket.htm If you're going to use a serious LNA then it'll require a separate 12v feed.

As for a BPF with the HF+: "You're having a Turkish".

Simon Brown, G4ELI

www.dxgalaxy.com
www.sdr-radio.com
www.sdr-satellites.com


-----Original Message-----
From: main@airspy.groups.io [mailto:main@airspy.groups.io] On Behalf Of Joe M.
Sent: 11 November 2017 23:54
To: main@airspy.groups.io
Subject: Re: [airspy] 4.5v software switched Bias-Tee from HF+?

For the minority who need LNAs, they can also add a DC insertion device or power them separately from the coax.

I agree "punishing" those who don't need Bias-T with additional loss is not something that should be done.

Joe M.





prog
 

On Sun, Nov 12, 2017 at 07:50 am, Eric Oyen wrote:
ok,
there are a number of solutions to getting max signal to the SDR.
1. mount at the antenna feed point. this will require remote power feed, a weather sealed box and a remote machine. Believe me, USB can't transport signals to the machine much past 12 feet (too much delay) so having a weather sealed machine close by won't hurt.

2. long run of very low coax (rg-6 works up to 1200 Mhz with fairly low loss). btw, there is a low cost LNA out there that can be powered on a USB connection. I ordered one earlier this year to use with one of my USB RTL-SDR dongles. it has good overload protection and adds only .5 Db insertion noise for 30 Db signal gain from 100 Khz to 5 Ghz. the thing is about the size of 4 postage stamps. this would be a good solution for long runs of coax.

so, unless you are doing anything above 500 Mhz, coax loss isn't going to be much of a factor. Thus, using the onboard LNA just seems like adding extra complication and noise.

DE n7zzt Eric
The third solution is to have a Raspberry Pi or Odroid near the antenna and power them with PoE (Power Over Ethernet). No loss, no latency, and even less CPU usage at the client computer.


jdow
 

facepalm
{o.o}

On 2017-11-12 07:50, Eric Oyen wrote:
ok,
there are a number of solutions to getting max signal to the SDR. 
1. mount at the antenna feed point. this will require remote power feed, a weather sealed box and a remote machine. Believe me, USB can't transport signals to the machine much past 12 feet (too much delay) so having a weather sealed machine close by won't hurt.

2. long run of very low coax (rg-6 works up to 1200 Mhz with fairly low loss). btw, there is a low cost LNA out there that can be powered on a USB connection. I ordered one earlier this year to use with one of my USB RTL-SDR dongles.  it has good overload protection and adds only .5 Db insertion noise for 30 Db signal gain from 100 Khz to 5 Ghz. the thing is about the size of 4 postage stamps. this would be a good solution for long runs of coax.

so, unless you are doing anything above 500 Mhz, coax loss isn't going to be much of a factor.  Thus, using the onboard LNA just seems like adding extra complication and noise.

DE n7zzt Eric

On Nov 12, 2017, at 1:32 AM, Simon Brown wrote:

FWIW I have 25m of good coax, using the LNA 5000 from SSB Electronics seriously degraded the received signals, I do mean *seriously*. Coax: https://messi.it/en/catalogue/50-ohm-cables-ham-radio/broad-pro-50-double-jacket.htm If you're going to use a serious LNA then it'll require a separate 12v feed.

As for a BPF with the HF+: "You're having a Turkish".

Simon Brown, G4ELI

www.dxgalaxy.com
www.sdr-radio.com
www.sdr-satellites.com


-----Original Message-----
From: main@airspy.groups.io [mailto:main@airspy.groups.io] On Behalf Of Joe M.
Sent: 11 November 2017 23:54
To: main@airspy.groups.io
Subject: Re: [airspy] 4.5v software switched Bias-Tee from HF+?

For the minority who need LNAs, they can also add a DC insertion device or power them separately from the coax.

I agree "punishing" those who don't need Bias-T with additional loss is not something that should be done.

Joe M.