EMRFD Message Archive 12058
Message Date From Subject 12058 2015-12-20 17:28:38 winston376 RF Analog Variable Time Delay Solutions
A question to the community....
Besides using cable delay lines or DSP/PC's, what other means of providing a variable time delay for RF ( 30 MHz max frequency) are available which can be implemented as an analog circuit?
Did some research and an old method was a bucket brigade architecture and older ICs but nothing found so far to address my needs.
Appreciate anything that can be suggested.
12064 2015-12-21 16:04:26 winston376 Re: RF Analog Variable Time Delay Solutions Don't know if my message got posted, so try again... 12065 2015-12-21 16:25:04 Andy Re: RF Analog Variable Time Delay Solutions "Don't know if my message got posted, so try again..."It was posted. Saw it.I don't know what sort of time delay range you are talking about (nanoseconds? milliseconds?) and if this is narrowband or broadband, but I can't think of much that does what you want. I know there are variable delay (or phase shift) devices for RF that are used in things like phased-array radars. Coax makes good RF delay lines, but not variable. And there are lumped (LC) delay line modules, some of them with selectable taps, but I think they have their own problems, and I'm not even sure how available they are anymore.Perhaps the lack of a response should tell you something. If someone asked me to make an analog variable delay for signals up to 30 MHz, I might shrug my shoulders.Andy 12066 2015-12-21 17:15:45 Will Re: RF Analog Variable Time Delay Solutions Hi,
Not very helpful ideas but several TV video delay lines in series would give variable delay in switched intervals.
Very early computers used mercury delay lines for their memory. Whether it would be feasible to send your signal along a thin glass/plastic tube filled with mercury and slide a current sensing pick-up along the outside to give a variable delay. However with the current frenzy abut the toxicity of mercury that might not be possible.
12067 2015-12-21 18:27:49 arfghans Re: RF Analog Variable Time Delay Solutions Data delay devices still makes some useful analog-capable parts that may be of use.
Tell us more about your specs and maybe we'll come up with other approaches.
12074 2015-12-22 06:11:02 firstname.lastname@example.org... Re: RF Analog Variable Time Delay Solutions
how long a delay do you want to be? do you want the delay to be constant across the bandwidth? what bandwidth are you looking for?
12076 2015-12-22 08:29:40 winston376 Re: RF Analog Variable Time Delay Solutions More detail on my application:
Homebrew small signal analog SSB receiver with signal values of -120 dBm and less. For demo purposes change from 30 MHz to 14.5 MHz maximum receive frequency. Want to delay signal by a minimum of 1 cycle (360 degrees). With an estimated 0.8 velocity factor at 14.5 MHz that's about 83 ns time delay.
Thanks for the responses so far. Appreciate any additional suggestions. Thanks. Alex
12077 2015-12-22 09:13:20 arfghans Re: RF Analog Variable Time Delay Solutions If it's basically a limited set of narrow bands you need to address, I'd start with a set of cable delays. RG174 doesnt take up much space and loss is low enough at HF. That simplifies the delay trim. Then maybe a commercial delay line or even a simple lowpass with varactor tuning (many varactors in parallel, if necessary) can add additional phase shift.
12078 2015-12-22 09:21:26 Tayloe, Dan (Noki... Re: RF Analog Variable Time Delay Solutions
You might look at what is on the net for phased vertical antenna arrays. I think they operate over a similar delay/phase shift range.
- Dan, N7VE
12079 2015-12-22 10:10:09 kb1gmx Re: RF Analog Variable Time Delay Solutions The easiest way is coaxial cable but RG174 that long at 30mhz is going to hurt (loss).A 360degree delay at frequency (30mhz) is 1 wavelength or ~10m correct for Vfactor using TFE cable you get it down to about 6M of wire (RG316).At 14.5 your in the 20m range (20.69m) and you would need 12.41m of rg316 cable for a 360degree delay.Its also possible to do lumped phase delays using 1/4wave filters cascaded, by varying the values you can get precise delays.What I don't see is what that has to do with somewhat weak signals at those frequencies.Allison 12080 2015-12-22 12:31:41 arfghans Re: RF Analog Variable Time Delay Solutions >The easiest way is coaxial cable but RG174 that long at 30mhz is going to hurt (loss).
No it's not. 1 WL of RG174 with PE dielectric at 30 MHz is 21 ft, loss is 1.2 dB. GL keeping the total loss of any other delay network that low.In any case, we're still missing a lot of requirements on this whole project...Gary, NA6O
12081 2015-12-22 19:44:56 Andy Re: RF Analog Variable Time Delay Solutions Alex wrote:"With an estimated 0.8 velocity factor at 14.5 MHz that's about 83 ns time delay."How's that?At 14.5 MHz, one cycle is 69 ns time delay, and it makes no difference what the velocity factor is. But the physical length of cable, to get 69 ns, does. You applied the velocity factor in the wrong place.This assumes 14.5 MHz is your ONLY frequency. If, on the other hand, you need 0-1 cycle at frequencies from 1.8 to 14.5 MHz, now you are talking about zero to 0.556 usec. Fortunately the longer delays are needed only at lower frequencies where the cable loss is less.Are you doing some sort of variable phase shift to do noise cancellation? That can be done more simply.Andy 12082 2015-12-24 16:36:03 kb1gmx Re: RF Analog Variable Time Delay Solutions I'm also confused about what being attempted.If the radio is SDR/IQ, opposite image suppressed, design then 90 degrees is the magic.That's easily done using simple twisted wire hybrid, RC, or LC networks.As to the time and distance its really very dependent on the VF or the coax and itvaries with materials, temperature and termination. Examples are foam types atabout .78 to .80, solid poly at about .66, and PTFE at .6. Even then same cabletype and different vendor is may be off by a percent or two. Generally you cutlong and dial it in using a VNA or resonance.The problem is if one wants a variable time delay then it gets a bit wild. Variabledelays are possible with analog systems but rarely used these days.Allison 12083 2015-12-26 15:11:43 Rod anyone making progress on surface mount R2? Greetings,
anyone out there making progress on a surface mount R2?
I would like to somehow contribute energy to that effort.
12084 2015-12-26 16:40:22 n2cqr Re: anyone making progress on surface mount R2? I am building an R2 now, but not surface mount. I'm having a lot of fun with it. I'm using an AD9850 DDS with quadrature output for the VFO. I have the mixers, diplexers and initial AF amps going. So it is now sort of a Binaural. Yes, I can hear the stereo effect. I'll build the 90 degree phase shift and AF amp next week.73 Bill N2CQR 12086 2015-12-27 00:22:32 brainerdd Re: anyone making progress on surface mount R2? Rod:I have been thinking for some time about adding the audio processor and audio amp circuits to my UHFSDR to make a self-contained unit. The R2pro is an improved design on the R2. I might be interested in doing a smt layout for the audio processor and an audio amp.My UHFSDR is similar to the down converter of the R2. I use ADE-1 mixers, Si570 with LVPECL output for the LO. The Q and /Q outputs of the Si570 go to a pair of LVPECL flip flops(guaranteed max toggle freq is minimum of 4 GHz!). With both a 0 and 180 degree output from the Si570, the I and Q generator circuit only needs to divide by 2. The LVPECL outputs then drive the mixers differentially through a 3dB pad.Kanga US sells through hole boards for bothe the R2 and the R2pro.Dave - WB6DHW 12088 2015-12-27 07:24:32 Graham Re: anyone making progress on surface mount R2? I keep looking at the Kanga USA site for news or stock of any of the R2
or R2pro kits and boards. Unfortunately there doesn't appear to be any
and there haven't been for quite some time, at least since Bill had a
stroke a few years ago. His web site does show stock of a very few
remaining kits plus some books. The kit documentation is still there
I exchanged a few emails with Rick (KK7B) a bit over a year ago about
some of his designs. At the time he was hopeful that kits would be
available through Kanga USA but it doesn't appear as though much has
We are all getting older and it is understandable that after a stroke
such as Bill has had that it takes a great deal of time to return back
to where one was before hand, if ever. Events like this gives one the
need to prioritize their needs and wants.
I have tinkered with some of R2 and R2pro like designs for a while but
never made a real concerted effort to finish anything. I guess I have
been waiting for the availability of nice kit with a PCB but it seems
that may not happen. I have also tinkered about with making my own PCB
but was always getting distracted with other projects. Perhaps it is
time to make a more concerted effort.
Rick has another very interesting design that is referred to as the iR2
instrumentation receiver which better suits my immediate interests. Time
to have a look at OSHPark.com again and revisit some of the available
PCB layout software.
For those interested in some of KK7B's writings, you can find much of
interest on his University web page:
whereupon you will find much food for thought.
cheers, Graham ve3gtc
On 2015-12-27 08:22, email@example.com [emrfd] wrote:
> I have been thinking for some time about adding the audio processor
> and audio amp circuits to my UHFSDR to make a self-contained unit.
> The R2pro is an improved design on the R2. I might be interested in
> doing a smt layout for the audio processor and an audio amp.
> My UHFSDR is similar to the down converter of the R2. I use ADE-1
> mixers, Si570 with LVPECL output for the LO. The Q and /Q outputs of
> the Si570 go to a pair of LVPECL flip flops(guaranteed max toggle freq
> is minimum of 4 GHz!). With both a 0 and 180 degree output from the
> Si570, the I and Q generator circuit only needs to divide by 2. The
> LVPECL outputs then drive the mixers differentially through a 3dB pad.
> Kanga US sells through hole boards for bothe the R2 and the R2pro.
> Dave - WB6DHW
12089 2015-12-27 09:10:55 Nick Kennedy Re: anyone making progress on surface mount R2? I'm close to complete on a phasing receiver that owes a lot to the R2. It's my first big surface mount project after finally getting into making boards using the toner transfer method.I'm using an Si570 and Tayloe detector, but a lot of other stuff comes from EMRFD and KK7B.Currently deciding how to package it and provide proper isolation where needed (my weak points). Then I'm sure some additional fine tuning will be required. After that I'll describe it on the web somewhere.73Nick, WA5BDU