Simple RF M4 Receiver - 315MHz Momentary Type[ID:1096] not working as expected

[kenRidge]

I recently purchased a Simple RF M4 Receiver - 315MHz Momentary Type[ID:1096] to work in conjunction with a Keyfob 2-Button RF Remote Control - 315MHz[ID:1391]. I have it connected to Adafruit Perma-Proto Mint Tin Size Breadboard PCB[ID:723]. I am trying to turn on a Diffused Red 10mm LED [ID:845] from about 15' away. I have the board powered by a 9V battery holder with switch & 5.5mm/2.1mm plug[ID:67]. The light works fine without the RF receiver in the loop, but when I attached the RF receiver and pushed the button on the keyfob I could only get about a 2 to 3 inch range. At about 1 foot the light would flicker if it came on at all. Any further away and the light would not come on at all.
Any suggestions?

[adafruit_support_bill]

Do you have the receiver antenna extended? For best results a vertical orientation is usually most effective.

It is also possible that the transmitter battery is weak. We've had a couple reports of that. See if a fresh battery helps.

[kenRidge]

OK, I fully extended the antena and put fresh batteries in the keyfob. Not much of an improvement. I get a solid light at about 1 foot away and a flickering light out to about 5 feet.

[adafruit_support_bill]

Alright. At this point it is a toss-up whether it is a transmitter problem or a receiver problem. Contact [email protected] with a link to this thread and we'll replace the set.

[kenRidge]

Will do. thank you for your help.

[kenRidge]

I received the new Receiver and keyfob. I got it to work out to about ten feet. I only need about another five feet to complete the project I set out to build. Is there anyway to boost the signal. I have to go through a wall and I wanted to put the receiver in a case to hide it.
So close but so very far away.

[adafruit_support_bill]

Have you tried pairing the old receiver with the new fob and vice-versa? You may find that a combination that works better.

[kenRidge]

Yes, I have tried switching all the products with the others. I even tried using both receivers at the same time,for some reason, but that did not help.

[adafruit_support_bill]

Are there any potential sources of interference nearby? WiFi access points? Cordless phones? Anything else in the 315MHz band?

[kenRidge]

It's entirely possible. The Phones in the office operate at 5.8 GHz. I'm not sure about the WiFi but I seriously doubt it is 315MHz. There might be other devices here that use that frequency. The signal seems to be worse in the front of the office as opposed to other areas. Unfortunately that is where I need my device that I have built.
Is there no way to boost this signal?

[adafruit_support_bill]

You may be able to fine-tune the receiver antenna. The ground-plane on these is pretty small and the antenna is located in the corner which is not optimal. And measuring the samples I have here, they appear to be a little longer than the theoretical ideal for a 1/4 wave @315MHz. (23.8cm)

But antennae are not really my area of expertise. I'll bounce this off a few of the other engineers to see if they have any suggestions.

[adafruit_support_bill]

Keven Townsend is our resident antenna expert and he had this to say:

If you want the best range, you really need a properly tuned front end with an impedance matching network, and I doubt they cared about this on a $2-3 board.

You could probably buy an edge mount SMA or RP-SMA connector, solder it into the edge of the board, and then put a proper 315MHz antenna, but again ... without the matching network who knows what kind of reflection is hapenning and how much signal loss there is.

Maybe a board edge connector like this if you can get a connection to GND as well (I don't have these boards so can't see the bottom side):

Molex 73251-1150
http://www.digikey.com/product-detail/e ... ND/1465156

Afterwards, find an SMA 315MHz antenna:
http://www.digikey.com/product-search/e ... a%20315MHz

A half-wave antenna is bigger but may give better results since it isn't as dependant on the GND plane ... 1/4 wave antennas have specific GND plane requirements. Unfortunately, DK only seems to stock 1/4 wave antennas (and 1/2 wave at 315MHz would be pretty big anyway).

I don't know what that will give you, but maybe it will help. It's going to be a questionable hack with impedance matching, though.

If you have the space, extending the antenna to 1/2 wave (47.6 cm) would probably be the easiest solution. You could either replace the existing wire, or solder an extension to it.

[adafruit_support_rick]

You're only getting 10 feet, line-of-sight? Or are there obstructions - walls, cubicle partitions, desks, etc? If so, can you locate the receiver and/or antenna so that it is clear of as many obstructions as possible? Higher up usually tends to be better.

[kenRidge]

Thank you for the advice. In looking for a 1/2 wave 315 MHz antenna this seems to fit the bill
http://www.digikey.com/product-detail/e ... ND/1958425
however after reading the data sheet
https://www.linxtechnologies.com/resour ... -cw-hw.pdf
I'm not so sure.
I am trying to send a wireless signal about 20ft through two walls that will simple activate a LED, is there another set-up I can use that work work better that you could recommend.

[adafruit_support_rick]

A directional antenna would be better than an omni-directional. But, if those are masonry walls, then the only thing that is really going to help is a more-powerful transmitter. Some garage-door openers are based on the same PT2262 encoder, and they might have a longer range.