Distance of remote

[Jon Slaughter]

I have a remote to a tv that I would like to increase its distance by a few
feet. The system is Dish TV and the remote uses UHF. I have taken apart the
remote and it uses

http://www.analog.com/UploadedFiles/Data_Sheets/ADF7901.pdf.

Unfortunately its SMT so its going to be hard to mess with. I need to know
exactly what I can modify to increase the range from about 50ft to about
55ft. I don't even know if this is possible though.

I figured that if I increased the current through the antenna that it could
give it enough.

Whats strange is that having the remote at very specific points and at very
specific angles in the room will get the signal to the reciever. I do not
believe this is due to reflections or anything like that. Maybe the signal
is degraded by the long distance so much that it only works 1/100 of the
time? It has steadily gotten worse over time and I assume its cause of the
batteries.

In any case I'm wondering what you guys think I can do? Maybe run a few more
batteries in it? Increase the loops of the antenna? Change the power going
to the transmitter section?

I'm going to read over the datasheet and see what I can come up with.
Unfortunately I do not think there is going to be a simple of a solution as
I initially thought.

Thanks,
Jon

 

[Jon Slaughter]

I have a remote to a tv that I would like to increase its distance by a few
feet. The system is Dish TV and the remote uses UHF. I have taken apart the
remote and it uses

http://www.analog.com/UploadedFiles/Data_Sheets/ADF7901.pdf.

Unfortunately its SMT so its going to be hard to mess with. I need to
know exactly what I can modify to increase the range from about 50ft to
about 55ft. I don't even know if this is possible though.

I figured that if I increased the current through the antenna that it
could give it enough.

Whats strange is that having the remote at very specific points and at
very specific angles in the room will get the signal to the reciever. I do
not believe this is due to reflections or anything like that. Maybe the
signal is degraded by the long distance so much that it only works 1/100
of the time? It has steadily gotten worse over time and I assume its cause
of the batteries.

In any case I'm wondering what you guys think I can do? Maybe run a few
more batteries in it? Increase the loops of the antenna? Change the power
going to the transmitter section?

I'm going to read over the datasheet and see what I can come up with.
Unfortunately I do not think there is going to be a simple of a solution
as I initially thought.

On the datasheet page 1 I have located the RFout side and I was wondering
what is the inductor for? Remove RF noise from VDD? and will increasing VDD
increase the range?

Thanks,
Jon

 

[John Popelish]

I have a remote to a tv that I would like to increase its distance by a few
feet. The system is Dish TV and the remote uses UHF. I have taken apart the
remote and it uses

http://www.analog.com/UploadedFiles/Data_Sheets/ADF7901.pdf.

Unfortunately its SMT so its going to be hard to mess with. I need to know
exactly what I can modify to increase the range from about 50ft to about
55ft. I don't even know if this is possible though.

I figured that if I increased the current through the antenna that it could
give it enough.

Whats strange is that having the remote at very specific points and at very
specific angles in the room will get the signal to the reciever. I do not
believe this is due to reflections or anything like that. Maybe the signal
is degraded by the long distance so much that it only works 1/100 of the
time? It has steadily gotten worse over time and I assume its cause of the
batteries.

In any case I'm wondering what you guys think I can do? Maybe run a few more
batteries in it? Increase the loops of the antenna? Change the power going
to the transmitter section?

The antenna (especially on the receiving end) is probably
the easiest thing to monkey with.

 

[John Popelish]

On the datasheet page 1 I have located the RFout side and I was wondering
what is the inductor for? Remove RF noise from VDD? and will increasing VDD
increase the range?

My guess is that it provides DC supply current to the output
stage.

 

[Jon Slaughter]

My guess is that it provides DC supply current to the output stage.

The output stage is the antenna? There is a dc blocking cap for obvious
reasons. It would seem that if I increased the RF VDD that it would supply
more current to the antenna and therefor increase the power dissipated by
the antenna which should increase the distance?

 

[Jon Slaughter]

The antenna (especially on the receiving end) is probably the easiest
thing to monkey with.

Not sure. Depends on what they use on the recieving end. If it was simply an
op amp or something then possibly but seeing they use SMT I'd still have
trouble. Also it would increase the noise and if thats the original issue
it wouldn't help much?

Thanks,
Jon

 

[john jardine]

On the datasheet page 1 I have located the RFout side and I was wondering
what is the inductor for? Remove RF noise from VDD? and will increasing VDD
increase the range?

Thanks,
Jon

The inductor XL is 50ohms at 350MHz and is used in preference to a load
resistor. Idea is that the PA stage can develop an A.C. signal voltage
across the inductor of nearly twice the supply rail voltage. Hence 4 times
the possible RF power out, as compared to a 50ohm resistor.

 

[Jon Slaughter]

BTW,

"The FSK_ADJ and ASK_ADJ resistors can be adjusted in the

system to optimize output power for each modulation scheme.

An additional 1.5 dB of output power is provided for the lower

bank of channels to adjust for antenna performance. The CE

line allows the transmitter to be powered down completely.

In this mode, the leakage current is typically 0.1 µA."



Which would seem to imply that I could easily change the power... except
probably they are using the maximum anyways.

 

[Gary Tait]

I'd play with the receive antenna first.

 

[Jon Slaughter]

BTW,

"The FSK_ADJ and ASK_ADJ resistors can be adjusted in the

system to optimize output power for each modulation scheme.

An additional 1.5 dB of output power is provided for the lower

bank of channels to adjust for antenna performance. The CE

line allows the transmitter to be powered down completely.

In this mode, the leakage current is typically 0.1 µA."



Which would seem to imply that I could easily change the power... except
probably they are using the maximum anyways.

Ok, looking at the circuit it seems they use



"15 RSET_OOK The value of this resistor sets the output power for data = 1
in OOK mode. A resistor of 3.6 kO provides the maximum output power.
Increasing the resistor reduces the power and the current consumption. A
lower resistor value than 3.6 kO can be used to increase the power to a
maximum of 14 dBm. The PA does not operate efficiently in this mode.

16 RSET_FSK The value of this resistor sets the output power in FSK mode. A
resistor of 3.6 kO provides maximum output power. Increasing the resistor
reduces the power and the current consumption. A resistor value lower than
3.6 kO can be used to increase the power to a maximum of 14 dBm. The PA does
not operate efficiently in this mode."



A value of 3600 ohms for pin 16 and 5*10^8 for pin 15. So it looks I cannot
adjust the power any better. I assume the OOK mode isn't used and this would
explain the high resistor value unless I'm misreading it. (says 548 on it I
think)

 

[Jon Slaughter]

Ok, looking at the circuit it seems they use



"15 RSET_OOK The value of this resistor sets the output power for data = 1
in OOK mode. A resistor of 3.6 kO provides the maximum output power.
Increasing the resistor reduces the power and the current consumption. A
lower resistor value than 3.6 kO can be used to increase the power to a
maximum of 14 dBm. The PA does not operate efficiently in this mode.

16 RSET_FSK The value of this resistor sets the output power in FSK mode.
A resistor of 3.6 kO provides maximum output power. Increasing the
resistor reduces the power and the current consumption. A resistor value
lower than 3.6 kO can be used to increase the power to a maximum of 14
dBm. The PA does not operate efficiently in this mode."



A value of 3600 ohms for pin 16 and 5*10^8 for pin 15. So it looks I
cannot adjust the power any better. I assume the OOK mode isn't used and
this would explain the high resistor value unless I'm misreading it. (says
548 on it I think)

I'm going to try and decrease the resistance of the 3.6kohms. IT says the PA
doesnt' work well but maybe it will give me enough.

 

[Jon Slaughter]

Ok guys, nm. Got it to work(atleast it looks like it). Paralleled a 10k
resistor with the 3.6k and it seemed to increase the power a bit more.
Works about 80-90% of the time instead of about 1-10% of the time. Might be
able to go a little lower but its good enough for now.

Jon

 

[Steve]

I have a remote to a tv that I would like to increase its distance by a few
feet.

Unfortunately its SMT so its going to be hard to mess with. I need to
know exactly what I can modify to increase the range from about 50ft to
about 55ft. I don't even know if this is possible though.
....
Whats strange is that having the remote at very specific points and at
very specific angles in the room will get the signal to the reciever. I do
not believe this is due to reflections or anything like that. Maybe the
signal is degraded by the long distance so much that it only works 1/100
of the time? It has steadily gotten worse over time and I assume its cause
of the batteries.

Are you saying it works reliably at 50 feet and hardly works at all at 55
ft? If so, then the math says adding less than 1 dB to the total RF power is
all you need. But I doubt that would be sufficient - the drop-off seems too
steep. I'd pay more attention to your other data that says specific
locations in the room are better than others. Sounds like multipath or a
local interference issue. How did you conclude its not due to reflections?
Have you tried moving the receiver around a bit (like a quarter wavelength)?
It might be easier than changing the circuitry if you only need it to work
in one seating location.

I've found certain rechargeable appliances can create havoc in the UHF
region for distances of 10 feet or so.- any battery chargers in the vicinity
(cordless vac, for instance)? Check opposite sides of adjoining walls too.

Steve

 

[Jon Slaughter]

Are you saying it works reliably at 50 feet and hardly works at all at 55
ft? If so, then the math says adding less than 1 dB to the total RF power
is all you need. But I doubt that would be sufficient - the drop-off seems
too steep. I'd pay more attention to your other data that says specific
locations in the room are better than others. Sounds like multipath or a
local interference issue. How did you conclude its not due to
reflections? Have you tried moving the receiver around a bit (like a
quarter wavelength)? It might be easier than changing the circuitry if you
only need it to work in one seating location.

I've found certain rechargeable appliances can create havoc in the UHF
region for distances of 10 feet or so.- any battery chargers in the
vicinity (cordless vac, for instance)? Check opposite sides of adjoining
walls too.

Steve

Well, I already fixed it last night and now its about 99% reliable. I do not
know if what I did is exceptable but it is working much better(for now).

Now if it was reflections I would still have the same issue but it
completely gone away. It was just out of its range for the power it was
using. Increasing the power increased the range. Was an easy fix but took
some time to figure out how to do it. Luckily the chip had the ability to
increase the power over its optimal setting and that the remote did not
already do that. It was simple as soldering in a resistor which was actually
kinda hard since I had to solder in an axial resistor onto a SMT resistor.
Wasn't to bad though.

I'm mainly worried about the long term effects of increasing the power. The
datasheet does not discuss the consequences. I'm not sure if it will just
drain the battery faster or if it could decrease the life of the circuit.