my grandpa was trained to fix the radio/radar equipment as i am told

JD,

The newer Mk. IV TDCs had the ability to accept range data from radar, but I think it was the from the ST radar on the observation scope. Most boats were not upgraded with the Mk. IV until after the war, even though it was developed in 1943, I believe.

There is a mod to manually input the range into the TDC, now.

Did the ww2 versions have the range rings?

Because of the difference betwen the way the PPI and A scope interpreted the signal, the PPI was pretty innacurate for range. This was the reason for the A scope. If the PPI was accurate, the A scope would not be needed.

Aye, you can enter range manually using this mod here.

http://www.subsim.com/radioroom/showthread.php?t=111371

Unfortunately the max range you can enter is 11,000 yds.

Well now... that is good news. And that's really all I was after.

Soooooo... nevermind. :)

JD

TDC Mk. IV had repeaters for both range and bearing inputs from SJ radar, not to mention TDC Mk. III could be field-modified into a Mk. IV setup. However, the important thing to note here is that the range and bearing inputs were manually entered with both the TDC Mk. III and Mk. IV. There was nothing "automatic" about sending range and bearing from either sonar or radar to the TDC; the difference in the Mk. IV was the addition of the SJ repeaters.

(And actually, that's a pretty simplistic description of how TDC Mk. IV worked; in reality it was quite a robust piece of equipment, even when compared to the Mk. III).

Very true. For our purposes it would be automatic, because the AI TDC operator would do this for us.

swdw, WWII radar did not have range rings. Someone posted a picture of the Cobia's SJ-1 radar earlier that only shows bearing lines. I recommend the bearing line mod, btw.

Yep. There were several methods to apply them. One was to take some thin paper (can't remember the name, like tracing paper) and draw lines on that. The other was to draw circles directly on the scope. You can read all about the operation of radar at hnsa, be careful though as there are numerous transcription / OCR errors, including numbered components being out of order for diagrams of the SD set, but specifcally the SJ radar is here:

http://www.hnsa.org/doc/radar/part4.htm

Here's an extract dealing with inking of the SJ PPI scope directly:


Bearings and ranges may he read approximately from the PPI scope without stopping the antenna. It is possible to obtain target course within 5 degrees, and target speed within 3 knots from this data. The following suggestions will speed the obtaining of data from the PPI and increase the accuracy:

1. Add inked circles on the face of the PH tube for estimating range (four solid circles, interspaced by four dotted circles). Care must he taken not to scratch the tube in any way.

2. Improvise a more accurate 360 degrees bearing circle over which rides a cursor, or thread stretched across the screen. Targets may then he split by this thread and hearing read on the circle.


The radar sets in SH4 are in some respects modelled oddly and in other ways modelled very well (e.g. target obscurance, wave obscurance and pip size depending on target angle are very good). I've also seen vastly varying ideas about what each set should do, some of these ideas are based on research and reading of submarines books and others are based on how the radar was modelled in other games. All the different ideas of what is correct was at the start quite confusing, especially mixed in with what was and wasn't right in SH4.

There's also confusion over how you would operate the radar sets. Reading the range of the SD radar tape is correct and rightly, really badly innacuarte. The SJ radar was much more precise - 25 yards plus or minus 0.1% of the range being measured. There's no way you can get anywhere near that level of accuracy by reading it off a tape.

Depending on what you think each scope is, your perceptions of what they should do will differ.

Is the left hand scope part of the SD or the SJ-1 radar? If you take it that it's the SD scope, then the range being read off the scale at the bottom is correct, but then it shouldn't rotate with the SJ radar head. It also shouldn't have a range selection switch (or sweep / focus). If you take it that the left hand scope is part of the SJ-1 radar, then it shouldn't have a range tape on it.

After extensive reading, the best I can make out is out of the SD and SJ radar sets, only the SD radar had a range marker switch to make the set draw (temporarily) a set of range lines, which could them be marked onto some tape stuck to the SD scope. Ranges of aircraft were then read directly from this tape and that was all the accuracy you had. The scope only had one range and that was from zero to 30 miles, with zero to 12 taking up the first half of the scope line and the remaining 18 miles getting squashed to the right. There are 3 units that make up the SD radar set.

The SJ radar set is comprised of 5 units. The PPI scope and the 'A' scope are not on the same unit. The 'A' scope is part of the 'Range-Indicator Unit' and does not have a range scale. After calibrating the unit to set the correct zero range, you can adjust the range crank on the seperate 'Range Unit', which moves a step on the 'A' scope on the 'Range-Indicator Unit' until the step on the 'A' scope is approximately touching the pip being measured. The 'sweep switch' is then turned to precision, which makes the 'A' scope display an expanded picture of 1,500 yards either side of the range step allowing for greater precision. This allows you to then move the range step towards the target pip until the beginning of the pip sits exactly in the corner of the step. When that has been done, the range can be read (digitally) from the seperate 'Range Unit'.

An approximate bearing can be read using either the 'A' scope and the hand crank's dial, or the PPI scope. A reading accurate to within a quarter of one degree can be obtained by lobe switching. This creates two spikes for the same target at slightly different ranges on the 'A' Scope and you then turn the hand crank until the two spikes are the same height, giving you an accurate bearing. Lobe switching is not modelled in the game.

This is all accurate to the best of my research. However, it's no problem at all to not include a digital range readout on the SJ set.

EDIT: About the 'A' Scope not being needed if the PPI scope were accurate, they would still need both, as although the PPI scope helps with situational awareness, by displaying land masses, that's also what makes it weaker. The land mass on the PPI scope saturates the picture and tracking air targets over land is only possible through the 'A' scope also when being jammed, the PPI scope is saturated / difficult to read, making the 'A' scope invaluable not only for seeing through the jamming, but also seeing what type of jamming it is. there's lots about this at the HNSA site. Very interesting, very well written too!

The A-scope we have is part of the SJ radar set. As to why it (incorrectly) has a range tape, my guess is the devs included it since the range display unit isn't modeled.

BTW, very nice description of how SJ and SD radar works! :up:

Radar operators reported the range to the TDC operator prior to the Mk IV. It worked great. This was a glaring omission by the devs. Apparently the send precise range to TDC command uses multiple pings. Looking into to whether that's the case or if it uses the radar.

Thank you for the response Nisgeis. Because I had to go through the Navy's ET A school before going to Nuc school, I actually understand everything you said.

I asked the questions regarding "realism" because this will be a great mod to add to RFB (with your permission) once it's finished.

Very good research- I respect that too. Keep up the excellent work!

Thanks swdw, I'm glad you asked the question, because it made me question it and as a result, I found out much more :up: . I now have a very good idea of how the 'A' scope on the range-indicator unit of the SJ set would have been switched over to the ST radar to find range, the range then appearing on the range unit and I didn't know that before I did that research for your question. If that is how it worked (and I haven't checked the ST specs yet) then if the SJ range and bearing could be sent to the TDC, then it follows that the ST radar could also.

@M. Sarsfield, do you have any pics of the USS Batfish's range unit? I have a sneaking susupicion that the digital read out is of the multiple wire filament readout type, where the filaments are all stacked on top of each other, rather than the wheels with numbers on type. Do you happen to have any pics of it?

@LukeFF - Do you have a copy of U.S. Submarines through 1945 by Norman Friedman, I think you've mentioned it before? I checked my copy and it says that the SJ-a range and bearing data could be fed automatically into the TDC (page 236 of my edition, in Chapter 12 -World War II). Now, by 'fed into' it doesn't explicitly state whether that means fed into the firing solution, or just fed into the unit for display. Where did the info about the range and bearing not being automatically sent come from, as I'd like to check it over. Unfortunately Norman Friedman doesn't give one of his excellent footnotes about the source of the information about the SJ-a set, so I can't look into that.

A while ago, I did read up on the TDC, though I can't remember whether I actually read the full blown manual or not. I do remember however that the TDC has bearing inputs for the sonar bearing and the periscope bearing, due to the parallax error of the spacing between the two. It would then follow that the TDC has to be told which input to take for the tracking (compensating for paralax as well). If the radar set can send the info to the TDC, it must be sent electrically, would it not be just a matter of selecting that repeater as the input to take for bearing?

At this point though it doesn't affect the mod, because I can't think of a way to get a send range/bearing button to work anyway, but as the matter has come up, I want to know now :D .

Oh yes, almost forgot. As far as the range rings goes, I haven't yet found any photos of any WW2 radar sets with field mod range rings inked on. If the manual advised it to be done though, I for one would do it because it would aid my at a glance ranging without having to stop the scope for a precise range on the 'A' scope.

The manual must have taken quite some time to compile and issue, so it's quite odd that they were advising of this field mod rather than attending to it during a refit. Perhaps the lines are on the inside of the CRT and the tubes had already been produced and could not be modified.

The USS Cobia's set doesn't have any range rings on it, but if the scope was restored, then it would have been cleaned and I'm sure india ink would come off with some alcohol, or perhaps it wore off through the years, or maybe it never had any range rings on it.

I'm not certain either way on the range rings and as the US Navy said it was optional, that's why I did my last mod as an option. About 33% of the downloads were for the bearing lines only. As it turns out though, the range rings I did were wrong and the ones the devs had on the PPIScale.dds graphic were closer to historic suggestion. I did find the range rings handy though, as when the target gets to the 25% ring, you know it's time to switch down a range scale. Very useful!

Maybe I'm reading it incorrectly, but this is what Norman says on page 240-241:

I see the reference you make on page 236. It makes me wonder whether those statements conflict, or they are talking about two different things.

I looked at the TDC manual, it's more about how it works internally and how to strip it and put it back together again. I'll keep looking for info.

Here's the arced contacts working. It doesn't work fully at the moment, but here's what it looks like now on zoomed in mode.

http://i251.photobucket.com/albums/g...darArcsWIP.jpg

It's odd how it changes the perception of what's happening. That's a radar image of a convoy true bearing 30 - 60 degrees (NEish). It's steaming on a course of 305 (NW). It's surrounded by destroyers, with a couple of fleet carriers, a cruiser and the Yamato in the centre. Spacing is at least 1km between ships. I think it's now easier to see the relative strengths of the returns, so the Yamato really stands out now.

To the south, there are three destroyers 500m apart at a range of about 8km. As they are so close, their radar images have merged. The destroyer on the right is head at a heading of 0 degrees (N), so has a smaller radar return than the destroyer heading 270 (W).

Ignore the colours for now, this is just the test colour, as it's easier to see green.

Contacts shown above have a 5 degree arc, to match the figures I found on the radar bearing resolution and beam width.

Next I'll work on the bearing lines, bearing numbers and range rings.

Holy frijoles that's looking good :o

Wow this looks sweet Nisgeis:ping:. The in game radar is definitely more complex than I realised. I never noticed that land masses obscured the radar (as it should) or that larger ships give a larger return on the screen. Coolies:rock:

It's a shame land mass doesn't give a radar return. That would be great to navigate in heavy fog close to the coast.

That's really looking good, thanks for working on this Nisgeis!

Good stuff!

now bout that Iff

i was also told it had a little pipper thing by the contact on the screen if it was a friend...