Questions on LNA
- Thread starter AngWay
- Start date
You'll probably get the most answers if you have your post moved to this forum:
forums.radioreference.com
Over there, you'll definitely get some really solid answers from @prcguy , @Ubbe and others. They have been a huge help in my adventures.
In the meantime, here are some really good threads that may help:
forums.radioreference.com
forums.radioreference.com
forums.radioreference.com
You could also look up the spec sheet for the SPF5189Z chip and see how it compares to those mentioned in the above threads.
Splitters, Filters and Multicouplers
For discussion of all inline devices used to split, combine or amplify a receive signal. This forum is not for any bi-directional (transmit) device. Use the Amateur or Commercial Radio forums for those.
Over there, you'll definitely get some really solid answers from @prcguy , @Ubbe and others. They have been a huge help in my adventures.
In the meantime, here are some really good threads that may help:
Bias-t & LNA
Hello RR, Currently having a Stridsberg 4 ports multicoupler and looking for a upgrade. Since I have 75' of lmr400 on a discone I will go with the LNA at the antenna and ZSFS-8-43 for the coupler. For the LNA I'm still looking around, ZX60-P103LN+ is interesting but I'm also wondering if you...
Yet Another Multicoupler Thread
This spring I plan a revamp of my tower mounted antennas. In advance of that, based on a lot of info gathered from RR, combined with the apparent unfortunately slowdown at Stridsberg Engineering, I've decided that going forward I'm going to build my own multicouplers. As has been hashed and...
Electroline Multicoupler
Looking at a couple of Electroline Multicouplers on Amazon. For VHF/UHF EDA2500MMA 4 Port EDA2900MMA 8 Port Other than the number of ports, is one better than the other?
You could also look up the spec sheet for the SPF5189Z chip and see how it compares to those mentioned in the above threads.
Ubbe
Member
The second link for the LNA show an LNA that are pretty good, especially at a $3 level. But it cannot be powered by bias-T. So you will have to buy two of those bias-T in the first link, one to power the coax with 5V DC, a standard USB voltage, at the scanner end and the other bias-T between LNA and the coax that goes to the scanner. It will give that 5V out of GND and DC solder points that you then connect to the LNA's GND and VCC.
But the result will be too much signal to the scanner and have to be attenuated. It doesn't mention its gain but are probably 20-24dB so you will have to calculate the coax attenuation and then put an attenuator between coax and scanner to reduce the signal to be 0 - +6dB or something like that. Maybe a 10dB or 15dB fixed attenuator can be used. There's also variable attenuators that you can set to a more exact value depending of how much signal the scanner can handle.
/Ubbe
These cheap LNAs and bias Tees don’t give all the specs in the advertising. They claim about 19dB gain @900mhz which is way too much but in my experience they have a lot more gain at lower frequencies like 10dB more and that could be close to 30dB gain at 100MHz which will cause more harm than good.
For a single receiver you don’t want to have much more than about 10dB gain from an LNA in front of it, otherwise be prepared for receiver overload, IMD, and worse reception. Using a 20-30dB gain amplifier then attenuating its output is not the best way as the extra gain of the LNA will only contribute to its own overload and IMD generation. You can’t make up antenna gain with LNA gain but with careful design and placement of the LNA near the antenna with appropriate filtering in front of the LNA you can improve reception a little.
Ubbe
Member
It's the same amplifier transistor used, SPF5189, that are used in a lot of LNA's, and all are identical in specs and for that $15 more you don't have to use that second $3 bias-T. It got a 27dB gain at 100MHz and 18dB at 900MHz according to a users review.
FM broadcast filters are always a good thing to use.
The scanner version that do P25 phase II are BCD996P2 and are also advanced enough to be upgraded to do DMR systems. It depends of where you intend to use the scanner, if it have the modes you need to monitor the system you'll want to hear. In many cases P2 systems are simulcast that can result in some issues to monitor them using this scanner.
/Ubbe
The BCD996T in the link does not do Phase II. The BCD996P2 is the upgraded version of this family which does handle phase II.
BCD996P2 - The RadioReference Wiki
does it do phase 1? also i see videos on how to enable bias tee on the rtl-sdr dongles by using files on a pc i have also noticed in sdrtrunk and sdrsharp their is a option to turn on and off bias tee i tried it before and it makes the little led light come on on my dongles. so my question is is using the software like sdrtrunk to enable bias tee enough and u don't have to use the files on the pc to enable and disable it? many thanks.The BCD996T in the link does not do Phase II. The BCD996P2 is the upgraded version of this family which does handle phase II.
BCD996P2 - The RadioReference Wiki
wiki.radioreference.com
is this a LNA based on just the advertisment? they look the same in the pictures but the wording is different.
See:
BCD996P2 - The RadioReference Wiki
Most of that no name china stuff is pure crap. Is your J Pole is not doing well?
Pretty sure when an lna is off and connected inline, most signals will not come thru, unless it has a bypass feature.
Pretty sure when an lna is off and connected inline, most signals will not come thru, unless it has a bypass feature.
What version of SDRTrunk are you running? When the light came on, did the noise floor or signals rise?
If the software has the feature to enable or disable and the dongle outputs enough power, it should work. This LNA I have requires 65ma to run and the Airspy mini only outputs 50ma.
yea i agree it is crap i think i'll just stick with the lana one with both bias tee and external power, i seen the one u have and the range is more of where i'm gonna be at i did buy This because i thought it would be hard to just not work maybe i'm wrong on it to. the version of sdrtrunk i'm using is 0.6.1 beta i'll add a pic of it but it lets me turn on and off bias tee, i don't have a lna yet but when i turn on the bias tee by it'self the signal doesn't change. as far as the j pole i have 100 foot of coax coming tomorrow then i'll be able to get it up higher. i went with kmr240 i hope thats good enough.
Attachments
the reason i asked if that one in the link does phase 2 is because i found one online for $55 but if it doesn't do p25 i don't need it. ThanksSee:
The BCD996P2 is compatible with APCO Project 25 Phases I and II. It also supports DMR and NXDN via paid upgrades.BCD996P2 - The RadioReference Wiki
Its one or the other. You should not use external power and bias t at the same time.
The Lana Wb is 300 mhz to 8 ghz. Aren't the sites by you in the 150/160 range?
I have the same version and neither Airspy (bias t capable) show the button. Hmm,
I missed this part
So yeah, without an LNA the signal won't change.
yeah 150/160 range but i also would like to monitor other freqs but 300 to 8 ghz would cover 150 range shouldn't it. thats strange your's doesn't have the bias tee button, i'm using the RTL-SDR V4 which ones are u using beside the airspy?
No, 150 is lower than 300. They advertise 300 to 8gig but I thought I did try it on 162 and 170 something and it worked. Going to try it over the weekend
The NooElecs I am using on this PC do not have the T (and are in use with Unitrunker) but I have a NooElec Smart Tee. Going to look at that over the weeked. I also have a HAckRf that has a T and it does not show it either.
That is weird maybe it's the brand idk please let me know when u find out. so it works on 150 and it shouldn't matter which one i buy? i'm on a budget and getting the wrong one will cause me needing to return it and all that jazz that i hate to do. oh and i tried unitrunker i spent several hours trying to get it to work but i couldn't .
That DC blocker i purchased on accident is there any use for that. like if i put that on with a LNA or just put it on by it'self what would it do?. reason i ask you is because u already know my stuation pretty good. many thanks
Ubbe
Member
That filter stops frequencies between 76-120MHz. If you listen to vhf-air below 120MHz it will not be suitable but if not needed then it covers the whole 88-108MHz band very well.
If you use a LNA at the antenna then you can use any coax as the LNA gain will compensate for it, even cheap and easy to route RG6 can be used. That excessive LNA gain at 100MHz and much lower at 900MHz, and also any coax will attenuate more at 900MHz than at 100MHz, can be compensated for by using a small 2pF-3pF capacitor in series with the signal before it enters your receiver, the SDR dongle you have now, that then will attenuate the signal much more at 100MHz than at 900MHz to even out the gain to make it more flat over its whole frequency range.
/Ubbe
cool good to know... what could i use This for in my setup does it have any purpose at all if i'm using a lna and a fm filter with a j pole listening to 150/160mhz? Thanks
