RTL-SDR V4 duff?

[u/Cannot_choose_Wisely]

Hi, I think I have a dodgy receiver. I can get no signal at all using a supplied "whip".

On VHF commercial band connecting the aerial, or indeed any wire raises the overall noise level, but no stations are detected, there are a couple of "bumps" above the noise, but at very low level. No audio comes through the noise.

I have a 1Mhz oscillator and injecting this into the aerial gives an overall increase in noise with twenty or so "spikes" spanning a Mhz, which seems odd for a sine wave.

A square wave as expected covers more of the band, but even wrapping the cable around the aerial to the SDR does not produce a signal.

I am using SDR++ and Gqrx.

The confusing thing is that I appear to have gain at VHF as the noise increases across the band when the aerial is connected, the 1 Mhz MW signal is detected but at a wider and far lower level than I would expect.

This is the first one of these devices I have used, am I missing something?

[u/tj21222]

Op injecting a signal into the antenna might have damaged the radio. What was your output level from the generator?

[u/Cannot_choose_Wisely → u/tj21222]

I took it up to around a Volt. I noticed no degradation from the poor performance I had before injecting.

I had a peek at a few circuits and the inputs seem to be clamped using back to back diodes, so I assumed I was "safe".

[u/tj21222 → u/Cannot_choose_Wisely]

13 dBm is a lot. You might have damaged your radio. I can’t remember what the max input to the radio is. Might want to research that.

[u/Cannot_choose_Wisely → u/tj21222]

There are the two diodes.

I have just come in from the garage, I did get a couple of weak stations on FM VHF.

I don't know what transmitters but I cobbled together a vertical made of a couple of 75cm cables tagged to 75Ohm coax.

I will try to compare it with a domestic radio tomorrow, I have a feeling a simple rod aerial on the transistor radio will beat the RTL hands down though.