# Thread: 940 Sensitivity Question

1. ## 940 Sensitivity Question

Despite bobdat's post, I have some questions about the 940 sensitivity. I just replaced my 25 year old Uniden RD9XL. I have three of the RD9s and know them and how they respond very well.

My question concerns the false alarms of the RD9 verses the 940. The RD9 gives a lot of false alarms and the 940 gives almost none. That should be good but it makes me question the sensitivity of the 940. The 940 will false alarm when I get close to automatic doors, like within 25-50 feet. The RD9 would have alarmed at 400-500 feet.

So, does the 940 have some logic in it that can discriminate between speed radar and door radar? If it does, does that logic break down at close range?

I haven't encountered speed radar yet (unless the 940 didn't report it) so I can't tell how sensitive the 940 is.

I can't run both at the same time because the RD9 triggers continuously, presumably on leakage from the 940. The 940 is quite.

I'm going to be traveling through some real treacherous territory, Rt 19 in WV. I need some confidence building for the 940.

Thanks

PeteC

2. Originally Posted by Petec
Despite bobdat's post, I have some questions about the 940 sensitivity. I just replaced my 25 year old Uniden RD9XL. I have three of the RD9s and know them and how they respond very well.

My question concerns the false alarms of the RD9 verses the 940. The RD9 gives a lot of false alarms and the 940 gives almost none. That should be good but it makes me question the sensitivity of the 940. The 940 will false alarm when I get close to automatic doors, like within 25-50 feet. The RD9 would have alarmed at 400-500 feet.

So, does the 940 have some logic in it that can discriminate between speed radar and door radar? If it does, does that logic break down at close range?

I haven't encountered speed radar yet (unless the 940 didn't report it) so I can't tell how sensitive the 940 is.

I can't run both at the same time because the RD9 triggers continuously, presumably on leakage from the 940. The 940 is quite.

I'm going to be traveling through some real treacherous territory, Rt 19 in WV. I need some confidence building for the 940.

Thanks

PeteC
First off do not run them together, I know most people have that urge, that detector will affect K on the Bel. As for the newer Bel it has much better filtering, so it will filter out alot of the junk your other detector picks up.

As for the short alerts on the Bel there is a couple of things first run it by itself and see how it responds to door openers, also if it is new it is prob an M4 platform which is more of an "on" axis design so it will pick up alerts more striaght ahead as opposed to 30 degrees and more.

3. Originally Posted by Petec
Despite bobdat's post, I have some questions about the 940 sensitivity. I just replaced my 25 year old Uniden RD9XL. I have three of the RD9s and know them and how they respond very well.

My question concerns the false alarms of the RD9 verses the 940. The RD9 gives a lot of false alarms and the 940 gives almost none. That should be good but it makes me question the sensitivity of the 940. The 940 will false alarm when I get close to automatic doors, like within 25-50 feet. The RD9 would have alarmed at 400-500 feet.

So, does the 940 have some logic in it that can discriminate between speed radar and door radar? If it does, does that logic break down at close range?

I haven't encountered speed radar yet (unless the 940 didn't report it) so I can't tell how sensitive the 940 is.

I can't run both at the same time because the RD9 triggers continuously, presumably on leakage from the 940. The 940 is quite.

I'm going to be traveling through some real treacherous territory, Rt 19 in WV. I need some confidence building for the 940.

Thanks

PeteC
Hi Pete,

Welcome to the forum!

Like focalcivic mentioned, don't operate both radar detectors at the same time. The old Uniden RD-9XL, a micro sized RD, emits a lot of noise from its local oscillator. 20 years ago RD manufacturers only were able to get good sensitivity in their micro designs by cranking up the power in the RD's Gunn oscillator. Thus your RD-9XL, when operating at the same time as your V940 (or most any other modern RD for that matter), will slaughter your V940's X and K band sensitivity.

Here is another example. A few weeks back I bought a \$40 Cobra ESD7000 just to play around with and to test if a cheap RD like the Cobra was even worth a penny of its cost. The cheap Cobra also uses an old style Gunn oscillator instead of a modern crystal controlled oscillator design. Running the cheap Cobra at the same time as either my Bel STi or my Escort 9500i slaughtered their K band sensitivities, and would cause the STi or 9500i to suddenly strongly alert to K band door openers only after I got really close to them. This sounds exactly like what you are describing, so I assume that you were using your RD-9XL at the same time as your V940.

If you weren't using your RD-9XL at the same time as your V940 and if the door openers which your V940 didn't alert to until you got really close to them, then I bet that the door openers in question were X band door openers. How can I guess this? Because all current Bel Vectors feature Bel's AutoScan technology. AutoScan intelligently filters multiple X band signals which are all roughly the same signal strength since AutoScan correctly assumes that these multiple X band signals are coming from door openers. The filter does get overridden once the signal strengths from these multiple X band signals pass a certain threshold which is approximately half way up the full signal strength display on the Vector. So, I bet that your V940 suddenly started alerting to the X band door openers with a signal strength of roughly 4 or 5 out of 10.

AutoScan also adds a full 1 second delay before alerting to weak signals, but does not add this delay when alerting to strong signals. The reason for the 1 second delay before alerting to weak signals is that, during that 1 second, AutoScan's filters do additional checks to see if the signal is a false caused by another radar detector -- namely Cobra radar detectors -- and checks to see if the signal is modulated -- cell phones, cell towers, microwave data transmissions, et cetera -- before displaying the alert.

So, the above is some info about the neat stuff built into your V940. Now, have some fun and find a K band door opener which is located close to the road. Most pharmacies such as CVS, Rite Aid and Walgreen's have K band door openers. Let the fun begin! Take runs towards the K band door openers first with your RD-9XL and then with your V940. You will see that the V940 has better range.

4. Originally Posted by MEM-TEK
Hi Pete,

Welcome to the forum!

Like focalcivic mentioned, don't operate both radar detectors at the same time. The old Uniden RD-9XL, a micro sized RD, emits a lot of noise from its local oscillator. 20 years ago RD manufacturers only were able to get good sensitivity in their micro designs by cranking up the power in the RD's Gunn oscillator. Thus your RD-9XL, when operating at the same time as your V940 (or most any other modern RD for that matter), will slaughter your V940's X and K band sensitivity.

Here is another example. A few weeks back I bought a \$40 Cobra ESD7000 just to play around with and to test if a cheap RD like the Cobra was even worth a penny of its cost. The cheap Cobra also uses an old style Gunn oscillator instead of a modern crystal controlled oscillator design. Running the cheap Cobra at the same time as either my Bel STi or my Escort 9500i slaughtered their K band sensitivities, and would cause the STi or 9500i to suddenly strongly alert to K band door openers only after I got really close to them. This sounds exactly like what you are describing, so I assume that you were using your RD-9XL at the same time as your V940.

If you weren't using your RD-9XL at the same time as your V940 and if the door openers which your V940 didn't alert to until you got really close to them, then I bet that the door openers in question were X band door openers. How can I guess this? Because all current Bel Vectors feature Bel's AutoScan technology. AutoScan intelligently filters multiple X band signals which are all roughly the same signal strength since AutoScan correctly assumes that these multiple X band signals are coming from door openers. The filter does get overridden once the signal strengths from these multiple X band signals pass a certain threshold which is approximately half way up the full signal strength display on the Vector. So, I bet that your V940 suddenly started alerting to the X band door openers with a signal strength of roughly 4 or 5 out of 10.

AutoScan also adds a full 1 second delay before alerting to weak signals, but does not add this delay when alerting to strong signals. The reason for the 1 second delay before alerting to weak signals is that, during that 1 second, AutoScan's filters do additional checks to see if the signal is a false caused by another radar detector -- namely Cobra radar detectors -- and checks to see if the signal is modulated -- cell phones, cell towers, microwave data transmissions, et cetera -- before displaying the alert.

So, the above is some info about the neat stuff built into your V940. Now, have some fun and find a K band door opener which is located close to the road. Most pharmacies such as CVS, Rite Aid and Walgreen's have K band door openers. Let the fun begin! Take runs towards the K band door openers first with your RD-9XL and then with your V940. You will see that the V940 has better range.

Smartie!

5. Originally Posted by djrams80
Smartie!
At least my screen name isn't something silly like Smarta\$\$!

6. Sorry, I didn't mean to confuse things. I was running them both, side by side only as the third step in a test. I wanted to see how they interfered with each other.

(Many years ago, when detectors were young, I remember following a car and watching his detector get triggered by mine and vis a versa. When his would stop blinking, mine would start. Then mine would stop and his would blink again. I assumed we each had scanning LOs and when his LO was at the right offset from my LO, mine would trigger, then the opposite with his.)

Now in my tests comparing the RD to the 940, I was using a Walgreen's as my source. When the 940, running standalone, alerted it reported "K band". To get this report I had to be in the 20-50 foot range and, now that you mention it, relatively "on axis". I had never considered the pointing angle to be that narrow. Interesting focalcivic, how-day-do-dat? Different antenna pattern; tough to do with a single horn antenna isn't it?

The RD, again standalone, would trigger at many hundreds of feet away from the same Walgreen's,

As for interaction when I tested the two together, note that I said the 940 was quite and the RD kept triggering. They were side by side, 1" apart and both facing forward. Unless the 940 was using some logic to ignore the RD, I would have to say the RD was more sensitive to the 940 emissions than vis a versa.

So, MEM-TEK, I think I did the first three steps of testing (against K band door openers),

(1) 940 alone (but no special consideration for axis)
(2) RD alone
(3) 940/RD interaction

Now I need to see if the sensitivity of the 940 is reduced in the presence of the RD. I might also see if I can find an X-band door and see if I can detect the Autoscan function.

Neat stuff, thanks guys.

Pete

7. Originally Posted by focalcivic
also if it is new it is prob an M4 platform which is more of an "on" axis design so it will pick up alerts more striaght ahead as opposed to 30 degrees and more.
x2, the new Belscort RD's do some pretty cool things to help reduce falses but still maintain real threat accuracy.

8. Originally Posted by MEM-TEK
At least my screen name isn't something silly like Smarta\$\$!
Yeah, that would be stupid!

9. Originally Posted by MEM-TEK
At least my screen name isn't something silly like Smarta\$\$!
Better than saying your ass is happy!

10. Originally Posted by MEM-TEK
If you weren't using your RD-9XL at the same time as your V940 and if the door openers which your V940 didn't alert to until you got really close to them, then I bet that the door openers in question were X band door openers. How can I guess this? Because all current Bel Vectors feature Bel's AutoScan technology.So, I bet that your V940 suddenly started alerting to the X band door openers with a signal strength of roughly 4 or 5 out of 10.
Beltronics Vector 940 doesn't have Autoscan.It's the only RD from Vector Series that does not have Autoscan.

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