Linked Questions

24
votes
4answers
13k views

What is the relationship between SWR and receive performance?

If an antenna analyzer shows 1:1, does that mean it's an ideal receiver as well? And what about the converse, will a well performing receive antenna show a 1:1 SWR? I've wondered this for a while, ...
3
votes
3answers
1k views

How do active loop vs. passive loop differ in terms of noise rejection?

As a urban ham (Harvard Square, Cambridge MA), I'm on the hunt for RFI rejecting antenna configurations. After hours of research, I've come across many strong recommendations for loop antennas, since ...
9
votes
2answers
2k views

High 40m noise floor during the evening but quiet in the afternoon

I've been dealing with S7 static on 40 meters ever since I got started a few weeks ago. It's so bad that I have to use my RF ATT so that the static is not deafening. I did some research about ...
3
votes
2answers
325 views

Can jamming a channel with white noise be detected?

If somebody were to setup a pirate radio signal that was broadcasting static would the people tuned in to that frequency be able to tell? Assuming that there was nothing already on that frequency ...
2
votes
3answers
284 views

Under what circumstances does intermodulation become an issue in a filter after LNA setup?

I'm reading about using software-defined radio for picking up ADS-B signals at 1090MHz. There is this blog which considers (among others) a setup as follows: ...
0
votes
2answers
316 views

Loop on ground for transmit?

If a large horizontal loop antenna, insulated but laying at ground level, works as an MF and low HF receive antenna, why (even though it has very high ground losses) can't it be used for transmit (to ...
1
vote
2answers
104 views

Increasing communication range by boosting output and input power

ORIGINAL QUESTION I am trying to increase the range of communication between two SDRs to simulate near space communication. The output power of TX is 10dBm but I would need 37dBm for near space ...
2
votes
2answers
123 views

How much dB gain do you need from an LNA in front of an antenna for great low-signal reception from satellites in the 2m and 70cm bands?

We are building a multi-stage LNA for a TR module we are building in the 144MHz and 440MHz range. This LNA we are considering (Qorvo QPL9547) provides about 22dB gain in the 2m and about 27dB in the ...
3
votes
2answers
160 views

Accounting for feedlines in noise temperature calculations

In writing an answer to "Use noise figure and gain to calculate weakest signal radio can receive?" I've managed to confuse myself. I believe this much is true: $$ T_\text{eq} =T_1 +{T_2 \over G_1} +{...
4
votes
2answers
143 views

Working satellite on 2 meters, at what arc distance to sun (center) will noise floor be problematic to a disruption of a communication path?

Is there some simple utility, or published set of charts, or suite of formulae, where one can approach the situation by inputting a space weather summary, (sunspots, various indexes, etc), the receive ...
4
votes
2answers
181 views

Use noise figure and gain to calculate weakest signal radio can receive?

An FM radio receiver, using a 1 kHz tone at 3 kHz deviation has a 12 dB SINAD (Signal To Noise and Distortion) of -116 dBm. I would like to increase the 12 dB SINAD sensitivity of the receiver to at ...
1
vote
3answers
117 views

Can a receiving antenna really be “as small as you can imagine”?

I read this antenna theory statement somewhere: And, for next-step or future thoughts: a receiving antenna can be as small as you can imagine, without loss of signal to noise. Is this BS or not?
1
vote
1answer
90 views

Lowest noise MMIC for HF? (160-20M)

I recently learned that these fancy modern ultra-low noise MMIC, while having <1dB noise figure around 1Ghz could be quite bad at low frequencies due to 1/f noise. What is lowest noise MMIC then ...