I found a 850-900 omni with 11 dbi and a 824-960 yagi with 15 dbi
All my RX path questions
- Thread starter Bonkk083
- Start date
Are there any 700 mhz systems of interest? If so finding something that resonates in the middle would be a good option.
No, just 851-866
Is this for a scanner or sdr? If scanner are there any simulcast systems close to you that you listen to and what scanner?
Scanner, a few simulcast, BCD536 and a 996P2
Using a high gain antenna on scanners not designed to handle simulcast could cause problems. I will let others chime in on that.
I gave the OP advice the other day to start learning Ham Radio and to meet or join his local Ham Club to start learning more about RF.
Ubbe
Member
Usually when running a semiconductor out of its specified voltage range will introduce negative aspects like more noise and less IP3 that create intermod issues. Always use the proper voltage and add an attenuator after the amplifier, just before the receiver, and preferable an adjustable one to get the exact right level for that receiver to get the best signal quality and lowest noise. Sometimes a receiver are overloaded even without an amplifier, that results in a worse sensitivity, and could use additional attenuation.
/Ubbe
I should have specified on the voltage. The LNA I have states 6 to 12 volts and I run it at 6. I definitely think I want an adjustable attenuator. Just have to figure out which one.
Ubbe
Member
Usually there's a voltage stabilizer in the amplifier that supply 3,3v or 5v to the actual amplifier device and then needs to be powered by at least 6v. Are you sure that the noise (and gain) increase at 12v? What amplifier is it? ScannerMaster has an adjustable attenuator with BNC connectors, that's the easy way to get one with the correct connectors.
/Ubbe
This is it. I do want to get the nooelec, rtl sdr or pga 103+ as anyone of those would most likely perform better.
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Ubbe
Member
Yes, you are right, at both accounts, it will change gain with voltage. It says max output +10dBm and has a 30dB gain. So extremely poor specification as PGA103+ and even Stridsbergs have at least +30dBm output and can tolerate higher signals much better. Remember that if you have no filters before the amp it will see FM broadcast, TV, cellular towers and everything else at its input and will overload very easily.
/Ubbe
prcguy
Member
30dBm output or IP1 would be 1 watt. Stridsberg rates their amps at 17dBm IP1, which is only 50 miliwatts, a far cry from 1 watt. The MiniCircuits version of the PGA103 seems to be the ZX60-P103LN and its rated around 22dBm IP1 or close to 158 miliwatts. Still way less than 30dBm. The MiniCircuits ZHL-1010 I like to use is rated 26dBm IP1 which is 398 miliwatts and works in places where the Stridsberg would fold up and die.
prcguy
Member
That is how much signal is lost in whatever path you have between the transmit antenna and receive antenna at the frequency you chose. An example of how you can use that might be starting with a 10 watt transmitter, which is 40dBm. Feed that to a 3dB gain antenna and you have an ERP (effective radiated power) of 43dBm or 20 watts. 43dBm ERP minus 109.5dB path loss is -66.5dBm at the receive antenna. If that receive antenna has 6dB gain you would have -60.5dBm of signal at the antenna output. If your coax loss is 2dB then you would have -62.5.5dBm of signal at your receiver. -62.5dBm is about 168 microvolts, which is a really strong signal to most receivers.
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Is less the number be better, the omni with 11 dbi was 109 and the yagi with 15 dbi was 105 I didn't know if that would tell me anything
prcguy
Member
For path loss the larger the number the more loss and the weaker signal you will have. More antenna gain can reduce the effects of path loss and so will more transmitter power.
What would the 9 dbd and 12.85 and 1.884 coax loss dbm numbers be
prcguy
Member
It would be a better signal than what I gave as an example above. A problem with terrestrial path loss calculations is they are not accurate due to signals bouncing of things making alternate paths between antennas. Signals can arrive from these multiple paths in phase and add more signal to your receiver or they can arrive out of phase and degrade reception. The amount of uncertainty can be 25dB or more. Most path loss calculations are based on free space and we don't live or operate our radios in space.
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